JPS6196175A - Ignition device of four-cycle internal-combustion engine - Google Patents

Abstract

PURPOSE:To mask an ignition signal in an exhaust stroke and prevent abnormal combustion, by equipping an ignition timing control means, which generates a masking signal of redetermined width synchronously with the ignition signal generated in the exhaust stroke, in the rotary shaft of an engine. CONSTITUTION:An ignition signal generating means 12 comprises a rotor 20 having a timing protrusion 19 on a crankshaft 3 and a pickup 21, and a device, equipping said means 12 and inputting an ignition signal generated in said means 12 to an ignition circuit 16 by the predetermined ignition timing through a trigger circuit 13, generates a spark in an ignition plug 18 through an ignition coil 17. While the device, equipping an ignition timing control means 14 comprising a rotor 23 having a timing protrusion 22 on a cam shaft 7 and a pickup 24, outputs in accordance with an output of said means 14 a masking signal of predetermined width through a masking circuit 15. And the device, when it generates the ignition signal in an exhaust stroke, operates so as to mask said ignition signal by said masking signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) This invention relates to an ignition device for a four-stroke internal combustion IaIAl engine, and more particularly to an ignition device for a four-stroke internal combustion engine that prevents electric sparks from flying to the spark plug during the exhaust stroke. It is.

(Prior Art) As is well known, in an ignition device for a Qi cylinder or a V-type twin cylinder among four-cycle internal combustion engines, an ignition signal generating means for generating an ignition signal every rotation of the crankshaft;
inducing a high voltage in the ignition coil by the ignition signal;
Some spark plugs are equipped with an ignition circuit that emits an electric spark.

This type of ignition device opens and closes the intake pulp and exhaust pulp by rotating the ignition signal generating means 1/2 turn in synchronization with the crankshaft so as to send an electric spark to the ignition plug only near the end of the compression stroke. It is conceivable to provide it on the camshaft, but since the cam chain, cam belt, etc. that connect the crankshaft and camshaft become slack, there is a risk that accurate ignition timing may not be obtained.

For this reason, the crankshaft is equipped with an ignition signal generating means, but in this case an ignition signal is generated every time the crankshaft rotates, and in addition to the prescribed explosion stroke, it also occurs at the top dead center of the piston during the exhaust stroke. A high voltage is induced in the ignition coil,
An electric spark will fly to the spark plug.

(Problem to be Solved by the Invention) As described above, even at the top dead center of the exhaust stroke of this type of four-stroke internal combustion engine, a high voltage is induced in the ignition coil, and a portion where the exhaust and intake overlap may occur. This may cause abnormal combustion or shorten the life of the spark plug.

This invention was made in view of the above circumstances, and has a simple structure that reliably prevents electric sparks from flying during the exhaust stroke, prevents abnormal combustion from occurring, provides smooth engine rotation, and enables the use of one spark plug. The object is to provide an ignition device for a four-stroke internal combustion engine that extends its life.

(Means for Solving the Problems) In order to solve the above problems, the present invention includes an ignition signal generating means that generates an ignition signal every revolution of the crankshaft;
inducing a high voltage in the ignition coil by the ignition signal;
In an ignition system for a four-stroke internal combustion engine that is equipped with an ignition circuit that sends an electric spark to a spark plug, a masking signal of a predetermined width is sent to an existing rotating shaft provided in the engine in synchronization with an ignition signal generated during the exhaust stroke. The ignition timing control means is provided, and the ignition signal is masked by the masking signal to prevent high voltage from being induced in the ignition coil during the exhaust stroke.

(Function) In the present invention, a masking signal of a predetermined width is generated by the ignition timing control means provided on the existing rotating shaft of one engine, and is outputted by the ignition signal generating means every revolution of the crankshaft. Of the ignition signals, the ignition signal that is output during the exhaust stroke is masked, so high voltage is not induced in the ignition coil during the exhaust stroke, and no electric spark will fly to the ignition plug.

In this way, the masking signal 1 generated from a simple ignition timing control means using an existing rotating shaft can prevent the generation of electrical sparks in the exhaust stroke, provide smooth engine rotation, and improve ignition timing. Extends the life of the plug.

(Example) Hereinafter, an example of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is a sectional view of a four-stroke internal combustion engine to which the present invention is applied.

In this figure, reference numeral 1 denotes a single-cylinder internal combustion engine, and a crankshaft 3 is rotatably supported on a crankcase 2 of the internal combustion engine 1. A cylinder block 4 is mounted on the crankcase 2, and a cylinder head 5 and a cylinder cuff pro are provided on the upper part of the cylinder block 4.

A piston (not shown) is fitted into the cylinder of the cylinder block 4 so as to be able to reciprocate. Rad to cylinder 5
A camshaft 7 is rotatably supported between the cylinder cup 6 and the crankshaft 3 in parallel with the crankshaft 3, and the camshaft 7 operates an intake valve and an exhaust valve by a well-known valve mechanism (not shown). There is.

The cam gear 8 of the camshaft 7 and the gear 9 of the crankshaft 3 are connected by a cam chain 10, and the rotational force of the crankshaft 3 is set to the camshaft 7 so that it rotates 172 times for every revolution of the crankshaft 3. has been done. As the camshaft 7 rotates, intake valves and exhaust valves (not shown) open and close at predetermined timing.

This internal combustion engine l is equipped with an ignition device 11, which includes an ignition signal generating means 12, a trigger circuit 13, an ignition timing control means 14, a masking circuit 151, an ignition circuit 1
6, an ignition coil 17 and a spark plug 18.

The ignition signal generating means 12 includes a rotor 20 provided on the crankshaft 3 and having a timing protrusion 19;
and a pickup 21 provided on the crankcase 2 opposite to the timing protrusion 19, which outputs an ignition signal when the timing protrusion 19 does not move past the pickup 21 due to one rotation of the crankshaft 3. This ignition signal is input to the ignition circuit 16 at a predetermined ignition timing via the trigger circuit 13, and induces a high voltage in the first ignition coil 17, causing an electric spark to fly to the spark plug 18 provided in the combustion chamber of the cylinder. It has become.

The ignition timing control means 14 consists of a rotor 23 having a timing protrusion 22 provided on the camshaft 7, and a pickup 24 provided on the cylinder cup 6 facing the rotor 23. When the protrusion 22 crosses the jack 24, a masking signal of a predetermined width is outputted via the masking circuit 15. The rotation of the camshaft 7 is set to be 1/2 rotation for each rotation of the crankshaft 3, and when an ignition signal is generated in the exhaust stroke, the masking signal is set to mask this ignition signal and send a high signal to the 1 ignition coil 17. No voltage is induced.

FIGS. 2 and 3 are circuit diagrams showing this ignition device in more detail.

FIG. 2 is a circuit diagram showing an example of a full-torque ignition system. In this circuit, an ignition voltage is applied from the ignition coil 17 to the ignition coil 17, and the primary coil 17a of the ignition coil 17 is grounded via the power transistor 26 of the ignition circuit 16. On the other hand, a spark plug 18 is connected to the secondary coil 17b.

The trigger circuit 13 includes an advance angle circuit 27, and the ignition signal output from the coil 21a of the pickup 21 constituting the ignition signal generating means 12 is input to the advance angle circuit 27. This advance angle circuit 27 is well known and applies an ignition signal to the base of the power transistor 26 in accordance with the rotational speed of the engine. When current flows through the base of the power transistor 26, conduction occurs between the emitter and the collector, and current flows through the primary coil 17a of the ignition coil 17.

Next, when the ignition signal goes low and the base current stops flowing, the emitter and collector are cut off. Therefore, the current in the primary coil 17a of the ignition coil 17 is cut off, and a high voltage is induced in the secondary coil 17b, causing an electric spark to fly to the ignition plug 18.

A masking circuit 15 is connected to the trigger circuit 13, and the masking circuit 15 is composed of a control transistor 28 and a flip-flop circuit 29. A control transistor 28 is inserted between the base of the power transistor 26 and ground, and a flip-flop circuit 29 is connected to the base of the control transistor 28. A pickup 24 constituting the ignition timing control means 14 is connected to the flip-flop circuit 29. A coil 24a is connected thereto.

The coil 24a of the pickup 24 outputs a set signal a and a reset signal S as shown in FIG. 4 when both ends of the timing protrusion 22 of the rotor 23 pass. When the set signal a is input, the flip-flop circuit 29 outputs a masking signal to maintain this state, and when the reset signal a is input, the flip-flop circuit 29 cancels the output state. Due to the output of the masking signal from the flip-flop circuit 29, a current flows through the base of the control transistor 28, and the emitter and
The collector is electrically conductive and connects the base of the power transistor 26 to prevent one ignition value from being applied to the base of the power transistor 26. This control transistor 28
conducts when the ignition signal is output during the exhaust stroke, thereby masking this ignition signal.

The output width of the masking signal is set to the maximum advance amount by the advance angle circuit 27, the maximum angle of the ignition signal, and the tolerance correction in the ignition circuit 16. determined by the width of

FIG. 3 is a circuit diagram showing an example of a capacitive discharge type ignition device.0 The AC output from a charging coil 30 placed in a generator (not shown) is rectified by a diode 31 and then connected to a capacitor 3.
A diode 33 and a thyristor 34 are connected between the diode 31 and the capacitor 32, respectively. The gate of the thyristor 34 is grounded via a resistor 35, and the resistor 3 is connected between the resistor 35 and the gate.
A lead angle circuit 27 is connected through the lead angle 6. Resistance 35.
36 protects the thyristor 34. Furthermore, a control transistor 28 similar to that described above is inserted between this resistor 36 and the advance angle circuit 27 and ground. A flip-flop circuit 2 is connected to the base of the control transistor 28.
9 is connected.

At a predetermined ignition timing, an ignition signal from the coil 24a of the pickup 24 is input to the gate of the thyristor 34 via the advance angle circuit 27 and the resistor 36 to ignite it, and the charge stored in the capacitor 32 is transferred to the ignition coil 17. Primary coil 1
7a, and the high voltage induced in the secondary coil 17b causes the spark plug 18 to generate an electric spark.

Next, the operation of this embodiment will be explained based on FIGS. 3 and 4.

When the crankshaft 3 rotates, a generator provided on the crankshaft 3 is driven to output AC power from the charging coil 3o. This AC output is rectified by a diode 31 and charged into a capacitor 32.

On the other hand, each time the timing protrusion 19 of the rotor 20 provided on the crankshaft 3 passes the coil 21a of the pickup 21 of the ignition signal generating means 12, an ignition signal is generated. Therefore, the ignition signal is generated at the crankshaft 3.
When the rotation angle is 1, for example, 0° near the end of the compression stroke, 3600° near the end of the exhaust stroke, and roughly 7200° near the end of the compression stroke. By the way, the camshaft 7 rotates at 172 times the rotation speed of the crankshaft 3, and the timing protrusion 22 of the camshaft 7 rotates at the pickup 2 of the ignition timing control means 14.
The timing at which the engine crosses the No. 4 coil 24a is set to the timing at which the ignition signal is generated in the exhaust stroke. Therefore, the masking signal from the masking circuit 15 is output before the ignition signal in the exhaust stroke is output, and makes the control transistor 28 conductive to prevent the ignition signal from being input to the gate of the thyristor 34. Therefore, since the thyristor 34 is not conductive, the generation of electric sparks in the spark plug 18 during the exhaust stroke is prevented, abnormal combustion is prevented, and smooth engine rotation can be obtained.In addition, the life of the spark plug 18 is extended. Further, the masking signal is set at a predetermined value, so that the rotation angle of the camshaft 7 is not affected even if a rotational error occurs due to slack in the cam chain 10 or the like.

On the other hand, since the ignition signal generated at the end of the compression stroke is not masked by the masking signal, it is input to the gate of the thyristor 34 and ignited, and the charge stored in the capacitor 27 is transferred to the primary coil 17a of the ignition coil 17. discharge through. Therefore.

An electric spark is generated at the spark plug 18 due to the high voltage induced in the secondary coil 17b.

The ignition timing control means 14 is arranged at a rate of 1/1 with respect to the crankshaft 3.
Although it is installed on the camshaft 7 that rotates twice, it is also possible to install a timing protrusion on an existing rotating shaft that rotates 1/4 and output a masking signal when the ignition signal is generated in the exhaust stroke. good.

(Effects of the Invention) As described above, the present invention provides an ignition timing control means for generating a masking signal for a predetermined portion in synchronization with an ignition signal generated during the exhaust stroke on an existing rotating shaft provided in a four-stroke internal combustion engine. This masking signal masks the ignition signal to prevent high voltage from being induced in the ignition coil during the exhaust stroke, so electric sparks do not fly to the spark plug during the exhaust stroke and abnormal combustion does not occur. Smooth engine rotation is obtained and the life of the spark plug is extended. In addition, since the masking circuit is generated with a simple structure using an existing rotating shaft, and the masking signal has a predetermined width, it is possible to reliably prevent the generation of electric sparks in the exhaust stroke. .

[Brief explanation of drawings]

Fig. 1 is a sectional view of a four-stroke internal combustion engine to which the present invention is applied, Figs. 2 and 3 are circuit diagrams showing this ignition system in more detail, and Fig. 2 shows an example of a full-torque ignition system. FIG. 3 is a circuit diagram showing an example of a capacitive discharge type ignition device, and FIG. 4 is a time chart showing the operation of the ignition device of the present invention. 3... Crankshaft 7... Camshaft 10
...Cam chain 11...Ignition device 12...
Ignition signal generation means 13...Trigger circuit 14...Ignition timing control means 15...Masking circuit 16...Ignition circuit 17...Ignition coil 18
...Spark plug Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A four-cycle internal combustion engine comprising an ignition signal generating means for generating an ignition signal every revolution of the crankshaft, and an ignition circuit for inducing a high voltage in an ignition coil by the ignition signal and emitting an electric spark to a spark plug. In the ignition system, an ignition timing control means for generating a masking signal of a predetermined width in synchronization with an ignition signal generated during the exhaust stroke is provided on an existing rotating shaft provided in the engine, and the ignition signal is masked with the masking signal. An ignition system for a four-cycle internal combustion engine, which prevents high voltage from being induced in the ignition coil during the exhaust stroke.