JPS6040865Y2 - Secondary voltage limiting device for ignition system for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for limiting the secondary voltage of an ignition coil for an internal combustion engine.

In a conventionally known configuration, for example, a contact type ignition circuit using a battery as a power source, no circuit for limiting the secondary voltage is provided.

In addition, in a circuit that uses a transistor instead of a contact, in order to keep the voltage generated by the primary coil of the ignition coil below the allowable voltage of the transistor when the current is cut off, a transistor protection circuit is installed between the collector and emitter of the transistor, or between the collector and base of the transistor. A constant voltage diode, etc. is inserted.

However, with the above-mentioned conventional devices, even in transistor type devices, for example, the battery voltage may rise abnormally, and the primary coil induced voltage when the primary coil is cut off increases.
It is merely used to protect the transistor from exceeding the allowable voltage of the transistor.

However, the maximum secondary voltage of the secondary coil of the ignition coil is set higher than the voltage required for the spark plug of the internal combustion engine to spark (hereinafter referred to as plug required voltage).

The reason for this is that since the ignition plug discharges, the voltage must of course be higher than the required plug voltage, but if the required plug voltage and the maximum secondary voltage are equal, even if a discharge occurs, this discharge will not ignite. Since this is only the generally-called capacitive discharge due to the charge stored in the distributed capacitance of the secondary coil of the coil, high-voltage cord, etc., it cannot be said to be sufficient to ignite the internal combustion engine mixed fuel.

Therefore, in order to appropriately distribute the magnetic energy stored in the iron core of the ignition coil by the primary coil current into capacitive discharge and inductive discharge during spark discharge, the secondary generated voltage is generally made as high as possible compared to the plug required voltage.

The larger this difference is, the larger the ratio of inductive discharge energy to capacitive discharge energy in the magnetic energy stored in the iron core will be, but since the secondary voltage will become very high, the shape of the ignition coil will need to be large. It has the disadvantage of being expensive.

Further, in the magnet generator type ignition device, since the voltage generated by the magnet generator is used as the ignition power source, there is a drawback that the secondary voltage inevitably becomes low at low speed rotation.

Therefore, in order to increase the secondary voltage, the number of turns ratio between the primary and secondary coils is increased by winding more secondary coils, but this increases the rotational speed and increases the voltage generated by the magnet generator. Since the secondary voltage is also very high, as mentioned above, the ignition coil has the drawback of being large and expensive.

In order to eliminate the above-mentioned drawbacks, the present invention provides a circuit that shorts when the secondary voltage reaches a predetermined voltage value, in parallel with the primary coil of the ignition coil, or with the auxiliary coil installed on the same iron core separately from the primary and secondary coils. By connecting the secondary coil and selecting the predetermined voltage value so that the secondary coil voltage is slightly higher than the plug required voltage, the secondary coil of the ignition coil can be When the voltage reaches the predetermined voltage, the primary coil or auxiliary coil is short-circuited to reduce the secondary generated voltage, and although the required plug voltage value is reliably generated, there is no excessive secondary voltage generated, making it compact. The object of the present invention is to provide a secondary voltage limiting device that can use an inexpensive ignition coil.

In order to improve the ignition of mixed fuel in the future, it is expected that it will be necessary to increase the induced spark discharge energy during discharge at the spark plug, but this will require an increase in the number of turns of the secondary coil and an increase in magnetic energy. In the conventional type, an abnormal increase in the secondary generated voltage is inevitable, but with the present invention, it is possible to suppress the abnormal increase in the secondary generated voltage.

In addition to the above, in the magnet generator type ignition system, in addition to the above, the secondary winding can be increased to meet the demand for higher secondary voltage at low speed rotations, and the secondary voltage can be suppressed by this invention at high speed rotations. In normal use, when the spark plug generates a discharge, it is possible to sufficiently supply the spark plug with inductive discharge energy.

The present invention will be described below with reference to embodiments shown in the drawings.

In the first embodiment shown in FIG. 1, 1 is a power supply battery, 2 is an ignition coil, 3 and 4 are primary and secondary coils, 5 is an interrupter, 6 is a capacitor, 7 is a spark plug, and 8 is a triac ( 9 is a constant voltage element (Zener diode), 10.11 is a voltage dividing resistor,
12 is a rectifier.

Next, the operation of the above configuration will be explained.

When the interrupter 5 closes, current flows from the battery 1 to the primary coil 3.

Next, when the interrupter 5 opens, a positive voltage is generated at the terminal of the primary coil 3 on the interrupter 5 side, and at the same time, a negative direction voltage is generated in the secondary coil 4, which is approximately -order and twice the turns ratio of the secondary coil. Occur.

Plug required voltage value of spark plug 7 (for example, 13 KV for internal combustion engines for two-wheeled vehicles, 24 KV for internal combustion engines for four-wheeled vehicles)
When the predetermined voltage value is slightly higher (2-wheel vehicle = 18 KV, 4-wheel vehicle = 28 KV), the constant voltage element 9 connected between the voltage divider circuit of resistor 10.11 and the gate of bidirectional thyristor 8
becomes conductive, current flows to the gate of bidirectional thyristor 8, and this thyristor 8 becomes conductive.

As a result, the primary coil 3 is short-circuited and the secondary voltage drops rapidly.

As a result, even if a spark discharge does not occur in the ignition plug due to an open circuit in the high-voltage cord, the secondary voltage of the ignition coil 2 will not exceed a predetermined value that is slightly higher than the required plug voltage. As the ignition coil 2, one having a small and inexpensive structure can be used.

FIG. 2 shows a second embodiment of the present invention, in which a generating coil 13 of a magnet generator is used as the ignition power source.

FIG. 3 shows a third embodiment of the present invention, in which the ignition coil 14 is built into the magnet generator by winding the primary and secondary coils 3.4 around the armature core of the magnet generator. It is designed to be used for both purposes.

FIG. 4 shows a fourth embodiment of the present invention, in which the output of the interrupter 5 is connected to the transistor 2 in contrast to the embodiment shown in FIG.
3.24 to amplify and intermittent the primary current of the ignition coil 2, and connect a semiconductor switching element consisting of a thyristor 8A in parallel with the primary coil 3 to amplify the secondary high voltage generated in the secondary coil 4. The voltage is detected by a voltage-detecting voltage dividing resistor 21 and a detection signal conversion transformer 22.

By appropriately setting the constants of the transformer 22 and the resistor 21, when the secondary high voltage exceeds a predetermined value, the signal detected by the transformer 22 exceeds the gate trigger voltage of the thyristor 8A.
When the primary coil 3 becomes conductive, the primary coil 3 is short-circuited.

Note that 25 and 26 are resistances.

FIG. 5 shows a fifth embodiment of the present invention, in which the capacitor 16 is charged via the rectifier 17 by the output generated by the capacitor charging coil 13 of the magnet generator, and the ignition timing is controlled by the output of the ignition signal generator 20. The present invention is applied to a capacitor discharge type ignition device in which the thyristor 19 is made conductive to discharge the charge in the capacitor 16 via the primary coil 3 of the ignition coil 2, and the secondary high voltage The configuration for detecting and short-circuiting the primary coil 3 is similar to the embodiment shown in FIG.

FIG. 6 shows a sixth embodiment of the present invention, in which the voltage generated by the secondary coil 4 is of opposite polarity to the embodiment shown in FIG. The secondary high voltage is detected by the constant voltage element 9, and in addition to the primary coil 3, an auxiliary coil 15 having almost the same number of turns as the primary coil 3 is provided in the ignition coil 2, and a thyristor 8A is connected in parallel with the auxiliary coil 15. It is connected.

According to this embodiment, when the secondary high voltage exceeds a predetermined value, the thyristor 8A becomes conductive and short-circuits the auxiliary coil 15, so that the voltage of the primary coil 3 becomes almost the same as the voltage of the auxiliary coil 15 due to the transformer action. By being limited to , the secondary generated voltage is limited to a predetermined value or less.

In each of the embodiments described above, the voltage dividing resistor 10.11 and the predetermined voltage element 9 or the voltage dividing resistor 21 and the transformer 22 are used as the voltage detection circuit, but the gate of the bidirectional thyristor 8 or the thyristor 8A is Connected to the secondary coil 4 via a resistor, bidirectional thyristor 8 or thyristor 8A
The gate trigger voltage may be used to detect whether the secondary high voltage is equal to or higher than a predetermined value.

Further, in each of the embodiments described above, the bidirectional thyristor 8 and the thyristor 8A are used as semiconductor switching elements, but transistors can also be used.

As described above, in the present invention, a semiconductor switching element is connected in parallel with the primary coil of the ignition coil or an auxiliary filter provided in the ignition coil separately from the primary coil to detect the secondary high voltage of the ignition coil. When this voltage reaches a predetermined value that is slightly higher than the required plug voltage, the voltage detection circuit immediately turns on the semiconductor switching element, resulting in excellent effects as described below.

(1) If the secondary coil terminal is opened, the secondary voltage will not become overvoltage.

(2) Since the secondary maximum voltage is suppressed to about the voltage required by the plug, the insulation resistance of the ignition coil may be relatively low, and the size can be reduced, resulting in low cost.

(3) In order to improve the ignition of the mixed fuel, it is necessary to increase the dielectric spark discharge energy during spark plug discharge, but this requires increasing the number of turns of the secondary coil and increasing the magnetic energy. However, with the present invention, it is possible to suppress the increase in the secondary generated voltage.

(4) In addition to the above, in the magnet generator type ignition system,
The demand for higher secondary voltage during low speed rotation can be met by increasing the secondary winding, and the present invention can suppress the secondary voltage during high speed rotation.

[Brief explanation of drawings]

1 to 6 are electrical circuit diagrams showing first to sixth embodiments of the device of the present invention. 2.14...Ignition coil, 3...Primary coil, 4...Secondary coil, 7...Spark plug, 8... Bidirectional thyristor as a semiconductor switching element, 8A...Thyristor as a semiconductor switching element, 9,10.11...
... Constant voltage element, voltage dividing resistor, 15... Auxiliary coil, 21.22...
・Voltage dividing resistor and transformer that make up the voltage detection circuit.

Claims (2)

[Scope of utility model registration request] (1) A semiconductor switching element that is connected in parallel with the primary coil of the ignition coil or an auxiliary filter provided in the ignition coil separately from the primary coil, and short-circuits the secondary coil or the auxiliary coil by being electrically connected. , further comprising a voltage detection circuit for detecting a secondary voltage generated in a secondary coil of the ignition coil and immediately bringing the semiconductor switching element into conduction when this voltage reaches a predetermined value slightly higher than the required plug voltage. A secondary voltage limiting device for an ignition system for an internal combustion engine. (2) The secondary voltage limiting device for an ignition device for an internal combustion engine according to claim 1, wherein the semiconductor switching element is a thyristor.