JPS6251756A - Ignition device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent generation of a spark except in the specified timing, by providing a means which emits accumulated energy in the primary coil side of an ignition coil when a switching means is cut off during a spark generation inhibited condition from a plug. CONSTITUTION:An ignition device turns on a power transistor Tr4 conducting an electric current to flow in the primary side of an ignition coil2 when a transistor Tr7 is turned off by a signal from a control circuit 6, while on the contrary, the ignition device cuts off the power transistor Tr4 generating secondary voltage in a secondary coil while a spark in a spark plug 3 when the transistor Tr7 is turned on by the signal from the control circuit 6. Here the ignition device provides a spark generation inhibited condition detecting circuit 10 detecting a condition that the spark must not be generated in the spark plug 3 from voltage of a power supply 1 or the signal of the control circuit 6. And the device, placing a transistor Tr11 in a cut-off condition by a signal of level L from the detecting circuit 10 during the spark generation inhibited condition, decreases voltage in the secondary side to prevent abnormal spark generation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an ignition device for an internal combustion engine, and particularly to an ignition device having a protective function suitable for preventing sparks from flying at timings other than those specified.

[Background of the invention]

In a conventional ignition system for an internal combustion engine, after the current flows to the ignition coil, the current is turned off at a time other than the specified timing, which may cause sparks to fly. This occurs, for example, when a cut-off signal is erroneously input to a power transistor that controls current flow to one ignition coil due to a drop in voltage. The sparks generated at this time cause a problem in that abnormal back torque is applied to the engine. For example, this phenomenon also occurs when the engine is started. Especially in the case of motorcycles, as the weight of the vehicle body has been reduced in recent years, the flywheel has also become lighter, so this back torque causes the tool itself to rotate the engine in reverse. There is a possibility that this may occur. Therefore, 1. For example, as shown in JP-A-55-137354, when a power-off signal is input to a power transistor at a time other than the specified timing, the power transistor is not cut off abruptly, but gradually. The idea of turning it off is known. However, in this method, the base current of the power transistor itself is controlled,
Since the current amplification rate of the power transistor is extremely large,
Even if you try to cut it off gradually.

The problem is that it is difficult to cut off so as to virtually prevent flying sparks.

[Purpose of the invention]

The object of the present invention is to, by a method different from the above conventional method,
An object of the present invention is to provide an ignition device for an internal combustion engine that can prevent flying sparks at times other than specified timings.

[Summary of the invention]

The present invention is provided with means for releasing the stored energy on the primary coil side of the ignition coil when the switching means is cut off during a state in which sparks from the plug are prohibited.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, 1 is a power source such as a battery, 2 is an ignition coil, 3 is a spark plug that is connected to the secondary side of the ignition coil 2 and sends ignition sparks to the internal combustion engine, and 4 is an ignition coil 2
A power transistor for controlling the flow and cutoff of a primary current, 5
A pulser outputs a signal in synchronization with the rotation of the internal combustion engine, and a control circuit 6 calculates and determines the conduction position and cutoff position of the power transistor 4 based on the signal from the pulser 5.

A transistor 7 and a resistor 8.9 form an amplifier circuit that transmits a signal from the control circuit 6 to the power transistor 4.

The above circuit configuration is a generally well-known ignition circuit for an internal combustion engine. Then, when the transistor 7 is turned off by a signal from the control circuit 6, the power transistor 4
is turned on, and current flows to the primary side of the ignition coil 2. Conversely, when the transistor 7 is turned on by a signal from the control circuit 6, the power transistor 4 is cut off, a secondary voltage is generated in the secondary coil, and sparks fly to the first spark plug 3.

Furthermore, the example of the present invention has the following configuration. That is, reference numeral 10 denotes a spark prohibition state detection circuit which receives the voltage of the electric current g1 or the signal from the control circuit 6 and detects a state in which ignition sparks should not be caused to fly to the spark plug. 11 and 12 are transistors, and 13 is a resistor, which constitute a switching circuit that conducts or cuts off the flywheel current of the primary winding of the ignition coil 2.

Now, in a normal normal state, the spark prevention state detection circuit 10 outputs a high level output. Therefore, transistor 11 is on and transistor 12 is on.
is off, and the ignition coil 2 is turned on and off by conducting and cutting off the power transistor 4. When the power transistor 4 is turned on and off, a high voltage is generated on the secondary side and normal operation is performed.

On the other hand, the sparks are prohibited, the signal from the sparks prohibited state detection circuit 10 becomes low level, and the transistor 1
1 is in the cutoff state will be described below.

The power transistor 4 is in a conductive state, and the ignition coil 2
When the primary current is flowing through the transistor 12, a reverse voltage is applied to the transistor 12, which is not particularly different from the conventional case.

However, when the power transistor 4 becomes conductive, a back electromotive force is generated on the primary side of the ignition coil, the transistor 12 is made conductive through the resistor 13, and the flywheel current due to the back electromotive force is Flow in the direction of the dotted arrow. Therefore, the primary side voltage due to the back electromotive force becomes a low value determined by the current amplification factor of the transistor 12 and the resistor 13,
This prevents the secondary voltage from rising and prevents sparks from flying to the spark plug.

Here, the spark prohibition state detection circuit 10 will be explained below.

The prohibition of flying sparks is carried out in various cases, and the first example is the prohibition of accidental flying sparks due to low power supply voltage.

This is to protect against the possibility that if the power supply voltage drops, the operation of the control circuit will become unstable and a spark signal will be output at an abnormal position, causing a malfunction such as erroneous ignition.

In other words, the voltage of the power supply 1 is input to the detection circuit 10, compared with a reference value, and when the voltage falls below the specified value, the control circuit 10
At the same time, the signal of the transistor E1 is set to low level, and even if the power transistor 4 is in the conducting state immediately before the control circuit 6 stops operating, the secondary coil side of the ignition coil 2 is turned off when the power transistor 4 is turned off. I'm taking care not to spread the flames.

A second example is energization and spark stop when the pulser 5 stops rotating.

This is to prevent the ignition coil current from continuing to flow after the engine rotation has stopped, and after a certain period of time has passed after the pulsar rotation has stopped, the ignition coil current is always turned off regardless of the operation of the control circuit 6. .

At this time, if the ignition coil current is turned off from the flowing state, sparks will fly to the secondary side, so the transistor 11 is turned off by the spark prohibition state detection circuit output, reducing the secondary side voltage and preventing abnormal sparks. . That is, as shown in the waveform of Figure 2, the charging/discharging circuit is driven by the pulser signal (A), and after a certain period of time after the pulser signal stops as shown in Figure (B), the charging/discharging circuit output level and the reference are changed. When the voltages match, the ignition coil current is forcibly cut off by the output (C) of the spark prevention circuit 10, and the transistor 11
is turned off to lower the secondary voltage of the ignition coil when the current is interrupted.

A third example is over-rotation prevention.

This prevents the engine speed from increasing too much by stopping sparks when the engine speed exceeds a specified value.

In other words, the rotation speed is detected by the interval of the pulsar signal, and when the rotation speed exceeds the specified speed, the transistor 11 is turned off by the spark prevention circuit output, and the secondary side voltage of the ignition coil is lowered to stop sparks, regardless of the control circuit output. , which prevents over-rotation.

Second aspect of the present invention. Third. FIG. 3 shows the fourth embodiment.

It is shown in FIGS. 4 and 5.

In each figure, parts with the same reference numerals as in FIG. 1 indicate equivalent parts.

FIG. 4 differs from FIG. 1 in that a thyristor 15 is used instead of the transistor 12. transistor 11
When the thyristor 15 is in a conductive state, the thyristor 15 is in a cutoff state and a high secondary voltage similar to the conventional one is generated in one ignition coil. When transistor 11 is cut off, puff-transistor 4
When the thyristor 15 is turned on due to the back electromotive force of the ignition coil 2, a gate current flows through the resistor 13 to the thyristor 15, turning it on and suppressing the back electromotive force to a low level.

Note that since the reverse withstand voltage between the gate and cathode of a thyristor is generally low, in this embodiment, a reverse current blocking diode 16 is connected in series to the cathode of the thyristor 15.

In the case of this embodiment, compared to the embodiment of FIG. 1, the thyristor has an advantage in terms of cost because it is easier to obtain elements with high breakdown voltage than transistors.

In FIG. 5, 18 is a transistor, and 17 is a constant voltage element.

When the transistor 11 is shut off, when the power transistor 4 is turned off from conduction, a base current flows through the transistor 18 due to the back electromotive force on the next side of the ignition coil, and the transistor 1
8 becomes conductive, the collector-emitter voltage of transistor 4 is held at a value determined by the voltage constant voltage element 17 and the pace-emitter voltage of transistors 18 and 4, and by flowing current in the direction of the arrow, the voltage is changed as in the case of Fig. 1. 1. Keep the ignition coil secondary voltage low to prevent spark plugs from flying.

The constant voltage element 17 allows current to flow through the transistor 18 only when a back electromotive force is generated in the ignition coil 2, and when the collector voltage of the power transistor 4 drops to the battery voltage, even if the transistor 11 is cut off, the current flows through the transistor 18. It is inserted so that it does not become conductive.

In the case of this embodiment, compared to the first embodiment, the flywheel current is passed through the power transistor 4 in common, so the transistor 1 used for switching
8 has the effect of requiring less capacity.

The fourth embodiment shown in FIG. 6 is different from the embodiment shown in FIG.
A thyristor 19 is used instead of the transistor 18.

Operationally, this is exactly the same as the case shown in FIG.

In the case of this embodiment, as in the second embodiment, compared to the third embodiment, the thyristor has a higher withstand voltage than the transistor, so it is advantageous in terms of cost.

In addition, 3rd. In the case of the fourth embodiment, in order to flow the flywheel current, the power transistor 4 for controlling large current flow is shared, but as shown in FIG. Connect in parallel on the primary side,
The same effect can be obtained by connecting the emitter of the transistor 18 to its base. Also, transistor 1
8, the cathode of the thyristor 19 shown in FIG. 5 may be connected.

〔Effect of the invention〕

According to the present invention, even if the power transistor 4 becomes conductive, the ignition coil stops one rotation after the current flows through it, the power supply voltage fluctuates, or other abnormal conditions occur, the spark will not fly out at a position other than the specified one. can be prevented.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the invention, and FIG. 2 is a circuit diagram showing a first embodiment of the invention.
Waveform diagrams showing operation examples of the spark prevention circuit, Figures 3 and 4,
5 and 6 show the second and third aspects of the present invention. 4th. FIG. 7 is a circuit diagram showing a fifth example. DESCRIPTION OF SYMBOLS 1...Battery, 2...Ignition coil, 3...Spark plug, 4...Power transistor, 5...Pulser, 6...Control circuit, 12,18.20...Transistor, 15 .17...Thyristor.

Claims (1)

[Scope of Claims] 1. An ignition device for an internal combustion engine, which includes a switching means for intermittent energization to an ignition coil, and a control means for controlling the timing of discontinuation of the switching element according to the rotation of the internal combustion engine. The invention further includes means for releasing the energy stored in the primary coil side of the ignition coil when the control means shuts off the switching means during a state in which flying sparks from a plug on the secondary coil side of the coil is prohibited. Characteristics of the ignition system for internal combustion engines. 2. In the device according to claim 1, the energy emitting means has a switching means arranged in parallel with the primary side of the ignition coil, and conducts the switching means to flow a flywheel current. An ignition device for an internal combustion engine characterized by: 3. The device according to claim 1, wherein the energy emitting means, after shutting off the switching means,
An ignition device for an internal combustion engine, characterized in that the switching means is re-energized to release the energy stored in the ignition coil. 4. In the device according to claim 1, the energy emitting means has a second switching means connected in parallel with the switching means, and conducts the second switching means to prevent the energy from being stored. An ignition device for an internal combustion engine characterized by releasing energy.