JPH0758065B2 - Internal combustion engine ignition device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine ignition device for generating a spark in a spark plug by a high voltage generated on a secondary side when a primary current of an ignition coil is interrupted intermittently.

[0002]

2. Description of the Related Art FIG. 1 conceptually shows a circuit of such an ignition device, in which a primary winding 2 of an ignition coil 1 is provided.
When the current flowing from the power source 3 is cut off by the contact 4, the spark plug 6 is driven by the voltage generated in the secondary winding 5.
Spark discharge to drive the internal combustion engine.

In FIG. 2, the primary current is cut off by a transistor 8 controlled by a control circuit 7, and a spark is generated in a spark plug 6 by a similar operation.

FIGS. 3A to 3C show waveforms of voltage and current in such an operation, and at the time point P, the contact 4 is closed or the transistor 8 is made conductive, so that FIG.
The ground voltage at the point A shown in Fig. 3 drops, and the current i flows through the primary winding 2 as shown in Fig. 3B. When the contact 4 is opened or the transistor 8 is cut off at the time point Q, the voltage at the point A rises and the current i flowing through the primary winding 2 is attenuated. Due to this change of i, the ground voltage at the point D is e _O = -L as shown in FIG.
It rises up to di / dt (L is the inductance). Ignition is performed by the high-voltage output voltage e _O on the secondary side of the ignition coil. On the other hand, also at the time point P, a reverse voltage e _R is generated due to the inductance. If this voltage e _R is applied to the spark plug 6, ignition explosion may occur in a process other than the explosion process originally required for the internal combustion engine, which may damage the engine.

As shown in FIGS. 1 and 2, a diode 9 is connected in series with the secondary winding of the ignition coil to block this reverse output voltage e _R.

[0006]

The reverse voltage e _R is usually several k.
Since it is V (1 to 5 kV), the diode 9 should have a withstand voltage exceeding it. However, assuming, for example, that the plug comes off from the grounded vehicle body while the vehicle equipped with the internal combustion engine is running, the voltage e _O shown in FIG.
Is not discharged by the spark plug and is charged to the stray capacitance 10.

[0007] Since the charge subsequent stray capacitance 10 when the voltage of the secondary winding 5 becomes 0 or a reverse voltage is applied in the reverse direction of the diode 9, is higher than e _O in order to prevent this voltage Withstand voltage, that is, generally 40 to
A diode having a withstand voltage of 50 kV or higher is required, which causes great difficulty in terms of manufacturing technology and price.

Further, even if the diode 9 withstands this voltage, the entire output voltage e _{O of} 40 to 50 kV is exposed without being discharged, which is a safety problem.

In addition to the case where the spark plug is disengaged in this way, the same problem occurs when the spark plug does not ignite due to some abnormality.

An object of the present invention is to solve these difficulties and problems, and to provide a safe internal combustion engine ignition device in which a high voltage is not exposed at the time of abnormalities such as when a spark plug is disengaged or when ignition is not performed. To do.

[0011]

In order to solve the above problems, in the present invention, a DC power source and switching means are connected to the primary winding of the ignition coil, and a diode is provided at one end of the secondary winding of the ignition coil. And a spark plug are connected in series, and a high voltage generated in the secondary winding when the primary current of the ignition coil is cut off is supplied to the spark plug through the diode, the diode is an avalanche diode, and the avalanche diode is used.・ The avalanche voltage of the diode is higher than the steady reverse output voltage generated in the secondary winding when the primary current of the ignition coil is applied,
And a voltage required to ignite the ignition plug, which is lower than the voltage required to ignite the ignition plug, and which is a high output voltage stored in the floating capacitance between the cathode side of the avalanche diode and the ground when the ignition plug is removed. It is a lower version.

[0012]

According to such means, the high voltage output voltage e _O when the spark plug comes off or when the spark plug does not ignite
Is not discharged and is stored between the cathode side of the diode and the ground due to the stray capacitance, and when the induced voltage of the secondary winding disappears, the high output voltage e _O stored in the stray capacitance applied in the reverse direction to the diode is , Is discharged to the avalanche voltage e _B through the avalanche diode and clamped to that voltage. As a result, the ground voltage on the cathode side of the diode becomes a low value (e _B ) and the danger is greatly reduced.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 4 is a voltage waveform of each part in one embodiment of the present invention using an avalanche diode.
Is the waveform at point D, (b) is the waveform at point B,
(C) is a voltage waveform between D and B.

The avalanche voltage of the avalanche diode used here may be about ₂ to 7 kV, which is ₁ to 2 kV higher than the steady reverse output voltage e _R of the ignition coil.

In FIG. 4, the two-dot chain lines U and S represent the waveform of each part in the steady state, and the one-dot chain line S and T represent the waveform when the spark plug is removed. The part is the waveform in a conventional diode.

First, in the steady state, the high-voltage output voltage e _O induced by the secondary winding 5 as shown by the alternate long and short dash line U-S is attenuated by the discharge of the spark plug. However, when the spark plug comes off, this high-voltage output voltage e _O is not discharged as shown by the alternate long and short dash line S-T, and
When the induced voltage of the secondary winding 5 accumulated on the point side disappears, it is applied to the diode 9 in the reverse direction. At this time, stray capacitance 1
The high-voltage output voltage e _O stored at 0 is discharged to the avalanche voltage e _B via the avalanche diode and clamped to that voltage. As a result, the ground voltage at the point _B becomes a low value (e _B ) and the danger is greatly reduced.

Since the avalanche voltage e _{B at} this time is higher than the steady reverse output voltage e _R by about ₁ to 2 kV, ignition does not occur due to the reverse output voltage during steady state when the spark plug is not removed.

[0018]

As described above, the internal combustion engine ignition device according to the present invention uses an avalanche diode as a diode inserted to block the reverse output voltage of the ignition coil, so that when the ignition plug comes off, etc. It eliminates the danger by clamping the high voltage output voltage of the ignition coil, which is exposed at the time of abnormality, and is economical because there is no need to use an ultrahigh withstand voltage diode, and the obtained effect is extremely large.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an example of a circuit of an ignition device in which the present invention is implemented.

FIG. 2 is a circuit diagram showing another example of the circuit of the ignition device according to the present invention.

FIG. 3 is a voltage / current waveform diagram of the circuits of FIGS. 1 and 2 in a steady state.

FIG. 4 is a secondary voltage waveform diagram of an ignition coil according to an embodiment of the present invention.

[Explanation of symbols]

 1 Ignition coil 5 Secondary winding 6 Spark plug 9 Diode

Claims (1)

[Claims] 1. A direct current power supply and a switching means are connected to a primary winding of an ignition coil, a diode and an ignition plug are connected in series to one end of a secondary winding of the ignition coil, and when the primary current of the ignition coil is cut off. In a device for supplying a high voltage generated in a secondary winding to the spark plug through the diode, the diode is an avalanche diode, and the avalanche voltage of the avalanche diode is a secondary winding when a primary current of an ignition coil is applied. Higher than the steady-state reverse output voltage generated in the above and lower than the voltage required to ignite the spark plug, and a high output voltage stored in the stray capacitance between the cathode side of the avalanche diode and the ground when the spark plug is removed. It is characterized in that it is lower than the voltage required to ignite the spark plug. Internal combustion engine ignition device.