JPH0118263B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ignition device for an internal combustion engine, and more particularly to a structure for controlling the duration of an ignition spark.

In spark ignition engines, it is difficult to ignite the engine at low speeds and low loads because there is a lot of residual gas. Furthermore, due to the recent trends in exhaust gas purification and the use of lean mixtures, improving ignition performance at low speeds and low loads has become an increasingly important issue.

One way to counter this is to lengthen the duration of the spark, for example to about 3 msec, which has been found to significantly improve ignition performance even under these conditions.

However, such a long spark duration is not only wasteful at high speeds or under high loads when ignitability is good, but it also has the disadvantage of significantly accelerating the wear of the spark plug electrodes.

According to our research, most of the wear on spark plug electrodes is due to discharge after the piston of an internal combustion engine has passed the top dead center of compression, and wear out before the top dead center of compression occurs. It was found that discharge hardly contributed to electrode wear.

This is thought to be because discharge in the presence of high pressure, high temperature, and flame accelerates electrode wear.

Moreover, according to our research, discharge after compression top dead center does not contribute to ignition at all.
Therefore, there is a need for an ignition system that does not cause the spark to continue past the top dead center of compression, but also maintains the spark for as long as possible at low speeds and low loads.

In order to solve such problems, conventional
As stated in Publication No. 29930, when the top dead center (TDC) position is reached, the primary coil is energized and the
It has been proposed to interrupt the next discharge. This device generates a first series of voltage pulses and a second series of voltage pulses, and calculates the second series of voltage pulses with a much larger number of pulses than the first series of voltage pulses at the rising edge of the first series of voltage pulses. to determine the ignition start timing, and
At the falling edge of a series of voltage pulses, the primary coil is energized and secondary discharge is cut off. The primary coil is OFF only while a spark is generated at the ignition start time and extinguished at TDC, and is ON during all other periods. Calculating the ON time and OFF time of the primary coil from the characteristic diagram shows that when the engine speed is 6000 rpm, the ON time is 4.3 ms at 1/2 rotation of the engine, and the ON time is ON at 0.7 ms.
OFF ratio 16%, ON time 8.9ms at 3000rpm,
OFF time 1.1ms, ratio 12%, at 600rpm
ON time is 48.3ms, OFF time is 1.7ms, and the ratio is 3.5%. Therefore, if this method of ignition control is performed at all engine speeds, there is a problem that the ignition coil generates heat and eventually burns out.

Therefore, the present invention operates the function of this system only at high engine speeds where the ignition frequency increases and the ON/OFF ratio increases, and activates the function of the conventional ignition system at low engine speeds. The purpose is to solve the above problem.

The present invention will be explained below with reference to embodiments shown in the drawings.
In FIG. 1, 1 is a battery whose negative electrode is grounded. 2 is the key switch and one end is the battery 1
It is connected to the positive terminal of. Reference numeral 3 designates a breaker contact as an ignition signal generator built into the distributor, one end of which is grounded, and the other end connected to one end of a resistor 4. The other end of the resistor 4 is connected to the base of a PNP transistor 5. The emitter of the transistor 5 is connected to the other end of the key switch 2. A resistor 6 is connected between the emitter and base of the transistor 5. transistor 5
The collector of is connected to one end of a resistor 7, and the other end of the resistor 7 is connected to the base of an NPN power transistor 8. The emitter of the power transistor 8 is grounded. A resistor 9 is connected between the base and emitter of the power transistor 8. The collector of the power transistor 8 is the ignition coil 1
It is connected to one end of the primary side of 0. The other end of the primary side of the ignition coil 10 is connected to one end of a resistor 11 in common with one end of the secondary coil. The resistor 11
The other end is connected to the other end of the key switch 2. The secondary coil of the ignition coil 10 is connected to a high voltage distributor 14 of the distributor.

3a is a disc built into the distributor and made of a magnetic material. Since this embodiment uses a four-cylinder internal combustion engine, the disc 3a is equally divided into four locations, and protrusions are provided at positions near the top dead center (TDC) of each cylinder. Sensor 3
b detects. This sensor 3b uses a known magnetic pickup. The output of the sensor 3b is connected to a discrimination switch circuit 12. The discrimination switch circuit 12 receives the signal from the sensor 3b.
A shaping circuit that shapes the TDC signal, a discrimination circuit that counts the number of pulses of this shaping circuit (the number of output pulses of transistor 5 may also be used) and outputs a signal when the rotation speed exceeds a set rotation speed, for example, 4000 rpm; It consists of a switch circuit that opens and closes depending on the output signal, and outputs a shaped TDC signal to the control circuit 13 when the engine speed exceeds the set speed. This control circuit 13 receives the signal from the discrimination switch circuit 12 and the signal from the breaker contact 3 as input, and generates a signal for controlling the primary current of the ignition coil 10. Its configuration is breaker contact 3
It is reset by the opening signal of the breaker contact 3 from the shaping circuit for preventing chattering from the switching circuit, and the TDC from the discrimination switch circuit 12.
It consists of a flip-flop circuit that is set by a signal.

Furthermore, if a TDC signal retard circuit (not shown) using conventionally known electronic advance device technology is inserted between the sensor 3b and the discrimination switch circuit 12 to configure a center dead center signal generator, the engine It is also possible to change the TDC signal generation position by controlling the TDC signal retardation circuit according to the rotational speed and engine load.

To briefly explain the operation of the above-described structure, first, the key switch 2 is closed, and the breaker contact 3 of the distributor is closed or opened as the engine is rotating. As a result, when the breaker contact 3 is closed, the transistor 5 becomes conductive, so that current flows through the resistor 7 and the base and emitter of the power transistor 8. Therefore, the power transistor 8 becomes conductive, and current flows through the primary side of the ignition coil 10 as a load. Next, breaker contact 3
When is opened, transistor 5 is cut off, power transistor 8 is cut off, and the primary current of ignition coil 10 is cut off. At that moment, a high voltage is generated in the secondary coil and a spark appears in the ignition plug. Figure 2 shows the waveform at this time. FIG. 2A shows the base voltage waveform of the transistor 5, and FIG. 2B shows the secondary high voltage waveform of the ignition coil 10 when the control circuit 13 does not operate.

On the other hand, a sensor 3b detects a signal from a disc 3a rotating in synchronization with the breaker contact 3. The output signal from this sensor 3b has two functions: engine speed and TDC position. Discrimination switch circuit 1
2, when the rotation speed exceeds a set rotation speed, for example 4000 rpm, a TDC signal is outputted as an output signal from the discrimination switch circuit 12. In this case, a hysteresis circuit is built in to prevent the output signal of the discrimination switch circuit 12 from chattering when the engine speed increases or decreases. Figure 2C
2 shows the output signal of the discrimination switch circuit 12 when the discrimination switch circuit 12 is activated.

The flip-flop of the control circuit 13 is reset when the breaker contact 3 is opened, and the flip-flop is set by the TDC signal from the discrimination switch circuit 12 to output the signal shown in FIG. 2D. This output signal drives the transistor 8 and controls the primary coil of the ignition coil 10. In this case, it is important to note that even if the primary coil is cut off and spark discharge occurs on the secondary side, when current is passed through the primary coil again, the spark discharge will stop.

In this way, spark discharge can be stopped near TDC, where combustion begins after the ignition spark hits the ignition plug. Figure 2 E shows the ignition coil 10-2 at this time.
Next is the high voltage waveform. As can be seen from FIG. 2, the spark discharge can be stopped for a time T.

Furthermore, as can be seen from Figure 2, the time during which the primary coil is cut off is within 1 ms, so if this control circuit 13 is activated when the engine speed is low, the primary coil is almost energized and is not connected to each other. It's getting old and it's not convenient, but the engine speed is
At high speeds of 4000rpm or higher, even a conventional ignition coil takes about 4ms to energize and 2ms to cut off, so even if this control circuit 13 is operated at around these rotational speeds, the power consumption and the heat generation of the ignition coil 10 will be lower than that of the conventional ignition coil. is equivalent to

In addition, in the case of low-speed rotation, spark discharge almost ends before TDC, so if the control circuit 13 is operated only at high rotation speeds where spark discharge continues even after TDC, it will have a great effect on preventing spark plug wear. becomes.

Further, in the above-described embodiment, the control circuit 13 is activated only by the engine speed, but the engine load condition is detected by the intake pipe pressure, and even if the engine load exceeds a certain load, the control circuit 13 is activated. If you let it work, it will be even more effective.

As described above, the present invention uses an ignition coil that generates high voltage for spark generation, which has a primary coil and a secondary coil, and detects the vicinity of top dead center of each cylinder in synchronization with the engine crankshaft. a top dead center signal generator that generates a TDC signal, a discrimination switch circuit that detects the engine rotation speed and outputs a TDC signal when the engine rotation speed is higher than a set rotation speed, and an output signal and ignition signal generation of the discrimination switch circuit. Since it is equipped with a control circuit that determines the conduction timing of the primary current of the ignition coil based on the ignition signal of the spark plug, when the engine speed is low, which does not have much effect on spark plug wear, the conventional ignition spark is generated and the spark plug is When the engine speed is high, which greatly affects wear, cutting off the ignition spark near TDC is practical and has the excellent effect of reducing spark plug wear.

Also, as long as the timing to start supplying the primary current to the ignition coil by the ignition signal from the ignition signal generator is set to a position delayed from the vicinity of top dead center, it is possible to determine whether or not there is a closing angle control device on the ignition signal generator side. Regardless of the situation, the present invention has the excellent effect of preventing wear of the spark plug electrode and preventing heat generation of the ignition coil at low engine speeds.

Furthermore, if the above-mentioned cutoff of the ignition spark is not fixed near TDC, but is varied depending on engine conditions, such as engine speed and engine load, there is an excellent effect of further reducing wear on the spark plug.

[Brief explanation of drawings]

FIG. 1 is an electric circuit diagram showing one embodiment of the device of the present invention, and FIG. 2 is a waveform diagram of various parts for explaining the operation of the device shown in FIG. 3...Breaker contact as ignition signal generator,
3a, 3b... Disk and sensor constituting a top dead center signal generator, 10... Ignition coil, 12... Discrimination switch circuit, 13... Control circuit.

Claims (1)

[Claims] 1. An ignition coil that has a primary coil and a secondary coil and generates high voltage for spark generation, and generates an ignition signal for determining when to interrupt the primary current of this ignition coil. an ignition signal generator; a top dead center signal generator that detects the vicinity of top dead center of each cylinder in synchronization with the rotation of the crankshaft of the internal combustion engine and generates a top dead center signal;
A discrimination switch circuit that detects the engine rotation speed and outputs the top dead center signal when the engine rotation speed is higher than a set rotation speed, and an output signal of the discrimination switch circuit and an ignition signal of the ignition signal generator to control the ignition coil and a control circuit for determining the conduction timing of the primary current of the ignition coil, the timing of starting the primary current conduction of the ignition coil by the ignition signal from the ignition signal generator is set to a position delayed from the vicinity of top dead center. An ignition system for an internal combustion engine characterized by: 2. Ignition of an internal combustion engine according to claim 1, wherein the discrimination switch circuit detects the engine rotation speed based on the top dead center signal of the top dead center signal generator. Device. 3. The ignition device for an internal combustion engine according to claim 1 or 2, wherein the top dead center signal of the top dead center signal generator changes depending on engine speed and engine load. .