JPS6243072B2 - - 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 an ignition device that increases the duration of a spark using a special principle.

In general, the so-called Ketarin type ignition system, which utilizes the induction effect of a booster coil, is widely used as an ignition system for internal combustion engines, but this is because the spark only occurs once when the point opens. , attenuation due to a drop in battery voltage at startup, attenuation due to a change in the impedance of the boost coil during high-speed rotation, engine sluggishness due to a delay in the rise of the boost coil during sudden acceleration, attenuation or misfire due to dirty plugs, etc., are inevitable, and the engine Not only is it not possible to fully demonstrate the performance of the engine, but it also has the drawback of increasing toxic exhaust gas. On the other hand, various types have been proposed in which a high-frequency oscillation circuit is coupled to the boost coil, and a high-frequency high voltage is induced on the secondary side while the point is off, thereby continuously generating sparks. . This type of ignition device has many advantages, such as a sustained spark, which reduces misfires compared to the Ketalin type, and eliminates the drop in spark voltage during high-speed rotation. However, on the other hand, if sparks are generated continuously while the point is off, the spark may not stop even after the engine's explosion stroke has passed and the point is on, resulting in unstable operation. In the case of low-speed rotation, there is a problem in that it may cause reverse rotation. Therefore, in the case of continuous sparks, for example, a time constant circuit consisting of a capacitor and a resistor is connected to the base of the transistor that makes up the high-frequency oscillation circuit, and even if the point is off, the oscillation can be stopped by charging and discharging the capacitor. However, the engine is constantly changing from low speed to high speed and from high speed to low speed, and it is extremely difficult to adjust the start and stop of oscillation to follow this change. At present, it has not been put to practical use because of the deviation in the falling edge and the resulting deviation in the ignition timing.

The present invention was made in view of the above-mentioned circumstances.
Another object of the present invention is to provide a new ignition device that is based on building up high pressure and lengthening the duration of the spark. Hereinafter, the content of the present invention will be explained in detail with reference to illustrated embodiments.

FIG. 1 is a basic circuit diagram of the present invention. In the figure,
SW is the engine switch, P is the point, L1 is the primary side of the boost coil, and L2 is the secondary side. T1
and T2 are switching transistors, and when one is on, the other is off.
T3 is a transistor that turns on and off the transistor T1 in synchronization with the opening and closing of point P, and R
4, R15 is a bias resistor that determines the operating point of the transistor T3. R1, R2, and R3 are bias resistors for the transistor T1, C1 is a bypass capacitor for the resistor R3, and R5 is a resistor that takes a resistance value that saturates the collector current of the transistor T2 when the transistor T1 is off. R6 is a resistor for fine adjustment of the base current of transistor T2,
C3 is a bypass capacitor for resistor R6. The collector of transistor T2 is coupled to the base of transistor T1 through resistor R7 and capacitor C2 to provide positive feedback.

Assume that the engine switch SW is now in the on state. In this case, when point P is closed, transistor T3 assumes an off state since its base current becomes almost zero, and therefore transistor T1 is also off. At this time, since the base current flows to the transistor T2 through the resistors R5 and R6, the transistor T2 is turned on, and the coil L1 and
Current flows through the series circuit of transistor T2. That is, if transistor T2 is replaced at the point indicated by the broken line, the series circuit of coil L1 and transistor T2 is exactly the same as the conventional Ketalin type, and coil L
1, the same amount of current will flow through the transistor T2 as would flow through the conventional point indicated by the dashed line.

When point P becomes open, a base current flows through transistor T3, turning on transistor T3, and following this, transistor T1 also turns on. As a result, the current passing through the resistor R5 flows through the path of the transistors T1 and T3, and the base current of the transistor T2 disappears, so that the transistor T2 is turned off. That is, the current in the coil L1 suddenly becomes zero, and a high voltage is induced in the coil L2. At this time, the rise of the high voltage of the coil L2 and the output are the same as in the conventional Ketalin type. At the same time, point P is opened and transistor T3 is turned on, so that transistors T1 and T2 start oscillating, and transistors T1 and T2 alternately turn on and off. Thereafter, when point P is closed, transistor T3 is turned off, returning to the initial state.

During the period when the transistors T1 and T2 repeat the switching operation, a high voltage is induced on the secondary side of the boost coil. The amplitude of this high voltage initially maintains a desired value, but as the back electromotive force of the coil L1 decreases, it gradually decreases and finally disappears. Therefore, the switching time (more precisely, the time required for the induced voltage in the booster coil to decrease to such an extent that sparks do not occur) may be determined so as not to cause problems when the engine rotates at high speed. In this way, there will be no delay in the rise of the voltage induced on the secondary side of the boost coil, no adverse effects of continuous sparks, no timing deviations, etc., and the duration of the spark will be longer, just like the conventional Ketalin method. Only.

Next, an embodiment of the present invention using the circuit shown in FIG. 1 will be described.

Engine speeds vary greatly from low speed to maximum speed, and if the spark duration is set short to accommodate the maximum speed, the effect of continuous sparking will be halved at low speeds. Figure 2 shows the low speed of the engine.
This is an embodiment in which the spark duration is changed according to high speed rotation.

In FIG. 2, the portion surrounded by broken lines has the same configuration as in FIG. 1. However, for convenience, some parts are omitted in FIG. 2. T4 is a transistor inserted between the resistor R5 and the power supply, and by turning it off, the switching operation of the transistors T1 and T2 is stopped. T5 is a transistor for turning on and off the transistor T4, and its control is achieved by turning on and off the transistor T5 by changing the potential of the capacitor C4. Capacitor C4 is connected to point P through diode D1, and the potential changes when point P is opened or closed. Resistor R8 is the base resistance of transistor T4, and resistors R9 and R10, together with capacitor C4, determine the on/off operation time of transistor T5 when the engine rotates at low speed. T6 is a transistor connected in parallel to resistor R9, and has the function of changing its internal resistance according to the rotation of the engine and automatically adjusting the on/off operation time of transistor T5.
R11 and R12 are bias resistors of the transistor T6, and C0 is a capacitor that changes the base potential of the transistor T6 in accordance with the rotation of the engine. Capacitor C0 is diode D0, resistor R0
is connected to point P through. The operation of FIG. 2 is as follows.

During the period when point P is closed, the base current of transistor T5 is approximately zero, and transistor T5 is in an off state. A base current flows through the resistor R8 and the transistor T4 is in an on state. In this state, when point P becomes open, transistors T1 and T2 start switching operations as explained in FIG. On the other hand, as point P becomes open, capacitor C4 is charged through resistor R10, and eventually base current flows through resistor R9 to transistor T5, causing transistor T
5 is turned on. When the transistor T is turned on, the transistor T4 is turned off and the collector current of the transistor T1 is cut off, so that the switching operation of the transistors T1 and T2 is stopped.
That is, the spark that has been continuing since point P became open disappears. Then, when point P is closed, the charge on capacitor C4 is transferred to diode D1
The transistor T5 is turned off and the transistor T4 is turned on.

Here, the time from when point P becomes open until transistor T5 is turned on, that is, transistor T4 is turned off, is determined by C4, R10, R9, and the collector-emitter resistance of transistor T6.
Therefore, by setting the collector-emitter resistance of transistor T6 to be high at low speeds and decreasing as the speed increases, the time from point P opening to transistor T5 turning on becomes longer at low speeds. , can be shortened as the speed increases. In FIG. 2, this is achieved as follows.

Capacitor C0 is charged through resistor R11 when point P is open, and charged through resistor R12, diode D0, and resistor R when point P is closed.
0, discharged through point P. The charging and discharging time constants of this capacitor C0 are C0, R11, R1
2, determined by the value of R0. This time constant is defined as follows: When the engine is running at low speed, the charge that is charged during the period when point P is open is almost discharged during the period when point P is closed; The value is determined so that the charge accumulated during the period can remain until the next point P closes. As a result, the potential of the capacitor C0 is low when the engine rotates at low speed (when the opening/closing operation of the points is slow), and increases as the engine speed increases.

When the engine rotates at low speed, the potential of the capacitor C0, that is, the base voltage of the transistor T6, is low.
The collector and emitter of the transistor T6 are almost in an open state, and it takes a long time from when the point P is opened until the transistor T5 is turned on. As the engine shifts to high speed rotation, the potential of capacitor C0 increases. This results in a reduction in the collector-emitter resistance of transistor T6, and the time from point P opening to transistor T5 turning on becomes shorter.

In other words, by adopting the configuration shown in Figure 2, it is possible to change the duration of the spark (longer at low speeds and shorter at high speeds) as the engine speed shifts from low speed to high speed. .

FIG. 3 shows another embodiment of the invention. In the case of Figure 1, if you forget to turn off the engine switch SW and keep point P closed, current will continue to flow through coil L1 and transistor T2, leaving point P open. , transistors T1 and T
3, the current continues to flow. In addition, if the power supply voltage (+V) abnormally rises above the rated voltage of the battery due to charging of the generator, etc., this will cause an increase in the back electromotive force generated in the coil L1 when point P is opened, and the spark will not continue. It is possible that the time taken is unusually long. FIG. 3 shows an embodiment that prevents problems caused by forgetting to turn off the engine switch or abnormally increasing the power supply voltage.

In FIG. 3, parts having the same functions as in FIGS. 1 and 2 are given the same reference numerals. Note that some of the circuits in FIG. 1 are omitted.
The transistor T5 is turned on when either the potential of the capacitor C4 or the collector potential of the transistor T7 rises. Capacitor C
4 is connected to point P via diode D1, and the potential changes when point P is opened or closed. Transistor T7 is turned on and off by the potential of capacitor C5. Capacitor C5 is connected to point P via diode D2. Diode D3 is for preventing the charge of capacitor C4 from flowing into transistor T7.

While the engine is rotating, a large amount of discharge from capacitor C4 flows through diode D1 to point P, and C4 and R1
Set it to 0. On the other hand, C5 and R14 are determined so that the potential of the capacitor C5 is maintained at a value sufficient to turn on the transistor T7 while the engine is rotating. Therefore, while the engine is running, transistor T5 is off and transistor T4 is on, achieving the operation described in FIG. 1. If you forget to turn off the engine switch SW and keep point P closed, capacitor C5
The electric charge of the resistor 14, the base of the transistor T7,
It gradually discharges through the emitter and finally turns off the transistor T7. When transistor T7 is turned off, its collector potential rises, transistor T5 is turned on, and transistor T4 is turned off. When the transistor T4 is turned off, the current flowing through the resistor R5 is cut off, and the transistors T1 and T2 are turned off.
If you forget to turn off the engine switch SW and keep point P open, the potential of capacitor C4 will rise, transistor T5 will turn on, transistor T4 will turn off, and in this case, transistors T1 and T2 will also turn off. state.

Next, there is a case where the power supply voltage (+V) increases abnormally, but in this case, the base current of transistor T6 is biased by resistors R11 and R12 to increase, resulting in a decrease in the collector-emitter resistance of transistor T6. . As explained in FIG. 2, this is equivalent to a decrease in the resistance value of resistor R9, and when point P is open, transistor T5
is turned on, and the transistor T4 is turned off quickly. This shortens the duration of the spark, and prevents the duration of the spark from becoming longer due to an abnormal increase in the power supply voltage.

As is clear from the above description, the ignition device of the present invention provides the following remarkable effects.

(1) The current cutoff on the primary side of the boost coil is the same as the Ketarin type, and the duration of the spark is simply longer during the period when the back electromotive force is generated in the coil, and there is no lag in ignition timing. , a powerful spark can be obtained continuously.

(2) The duration of the spark changes as the engine moves from low speed to high speed, so
This can prevent insufficient spark duration when rotating at low speeds and, conversely, from exceeding it when rotating at high speeds.

(3) Even if you forget to turn off the engine key, the current of the boost coil etc. can be automatically cut off regardless of whether the points are open or closed, and even if the power supply voltage rises abnormally, the spark duration will not be extended beyond the specified limit. do not have.

(4) Existing boost coil can be used as is.

[Brief explanation of the drawing]

FIG. 1 is a basic circuit diagram of the present invention, and FIGS. 2 and 3 are circuit diagrams of an embodiment of the present invention using the circuit of FIG. SW...engine switch, L1, L2...boost coil, P...point, T1-T7...transistor, R0-R13...resistance, C0-C5...
...Capacitor, D0-D3...Diode.

Claims (1)

[Claims] 1 comprises first and second transistors that are connected in cascade and are switched into opposite states, and a third transistor that is turned on and off depending on the open/closed state of a point, and the first transistor is connected to the third transistor. the second transistor is connected to the primary side of the boost coil, and the connection point between the boost coil and the second transistor is connected to the first transistor through a capacitor and a resistor. In an ignition device for an internal combustion engine, the ignition device is connected to a base, and induces a high voltage on the secondary side of a boost coil as a point becomes a first state, and then repeatedly induces a high voltage with a damping characteristic. a fourth transistor connected between the transistor and the power source; a control circuit that turns on the fourth transistor when the point is in the second state and turns off the fourth transistor when the point is in the first state; 1. An ignition device for an internal combustion engine, comprising: a time adjustment circuit that changes the time at which the point is turned off in accordance with the opening/closing cycle of the point.