JPH04191465A - Ion current detection device - Google Patents

Abstract

PURPOSE:To detect the ion current without using a large and expensive DC-DC converter by providing a capacitor, which is charged by the high voltage for ignition, for applying the positive bias voltage to an ignition plug with this charged voltage. CONSTITUTION:At the ignition time of an internal combustion engine, the negative high voltage for ignition is generated in a secondary coil 1b of an ignition coil 1, and the discharge current is flowed to a passage showed with an arrow to generate the discharge between electrodes of an ignition plug 3, and the air-fuel mixture of the internal combustion engine is ignited. A capacitor 7 is charged with the polarity showed in a figure by this discharge current. The ionization work is generated with the combustion of the air-fuel mixture to generate the ion current, and since the ion current is flowed by the movement of the electron caused by the positive bias of the capacitor 7, the voltage, which is generated in an output terminal 9 by the generation of this ion current, is detected to confirm the combustion of the air-fuel mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ion current detection device used, for example, in detecting a misfire in an internal combustion engine.

[Conventional technology]

An example of this type of device, which has already been filed by the present applicant, will be explained with reference to FIG. In the figure, l is the primary winding 1
a, an ignition coil having a secondary winding lb, 2 a power transistor connected to the primary winding 1a and for intermittent primary current, and 3 connected to the secondary winding lb to which a high voltage for ignition is applied. A spark plug (not shown) ignites the air-fuel mixture of an internal combustion engine; 4 is a power source serving as bias means for applying a positive bias voltage to the spark plug 3; 5 is connected in series to the power source 4; A resistor 6 for converting the ion current into voltage is an output terminal for detecting the voltage generated in the resistor 5, and together with the resistor 5 constitutes an ion current detection means.

In the configuration as described above, when the power transistor 2 is turned off at the ignition timing of the internal combustion engine, and the primary current of the -order winding 1a is cut off, a high voltage for ignition of negative polarity is applied to the secondary winding lb. This generates a discharge between the electrodes of the spark plug 3 and ignites the air-fuel mixture of the internal combustion engine.

At this time, ionization occurs as the mixture burns, and ions are generated. Here, the electrode of the spark plug 3 acts as an electrode for detecting ion current after the above-mentioned discharge, and an ion current flows due to the movement of electrons due to the positive polarity bias of the power source 4. Combustion of the air-fuel mixture can be confirmed by detecting the voltage generated at the output terminal 6 due to the generation of this ion current.

[Invention or problem to be solved]

In the configuration as described above, the power supply is normally 5
Since 0 to 300V is required, is there a way to boost the voltage using a DC-DC converter? This requires a transformer, which makes the device larger, heavier, and more expensive. There was a point.

This invention was made to solve the above-mentioned problems, and an object thereof is to obtain an ion current detection device that is small, lightweight, and inexpensive.

[Means to solve the problem]

The ion current detection device according to the present invention is provided with a capacitor that is charged with a high voltage for ignition and applies a positive bias voltage to the spark plug using the charged pressure.

[Effect]

The capacitor in this invention is charged to a sufficient voltage by a high voltage for ignition, and this charging voltage applies a positive bias voltage to the spark plug.

[Embodiment of the Invention] An embodiment of the invention will be described below with reference to FIGS. 1 and 2. In the figure, 7 is a capacitor connected to the positive polarity side of secondary winding lb, 8 is a resistor connected between capacitor 7 and ground and converts the ionic current into voltage, and 9 is the voltage generated in resistor 8. It is an output terminal for detecting the ion current, and together with the resistor 8 constitutes an ion current detection means. 10 is a diode connected in parallel to the resistor 8, and 11 is a Zener diode connected in parallel to the capacitor 7.

In the configuration as described above, a negative ignition high voltage (approximately -1
A discharge current flows along the path shown by the arrow in FIG. 2(a), causing a discharge between the electrodes of the spark plug 3 and igniting the air-fuel mixture of the internal combustion engine. Further, the capacitor 7 is charged to the illustrated polarity by this discharge current. Note that the charging voltage of the capacitor 7 can be arbitrarily set using the Zener diode 11.

At this time, as in the conventional device, ionization occurs as the air-fuel mixture burns, and ions are generated. Here, capacitor 7
Due to the movement of electrons due to the positive polarity bias (approximately 50 to 300 V), an ion current flows in the path shown by the arrow in Figure 2 (b), and the voltage generated at the output terminal 9 due to the generation of this ion current is detected to cause mixing. You can check the combustion of Qi.

In the above-mentioned embodiment, a device that generates a high voltage for ignition of negative polarity has been described, but a device that generates a high voltage for ignition of positive polarity may be used, and will be explained with reference to FIG. 3. In the figure, the discharge current is secondary winding 1b → diode 12 → spark plug 3 → ground → diode 10 → capacitor 7-
°Secondary winding] Flows along path b. At this time, capacitor 7
is charged to the polarity shown. Also, the ionic current is capacitor 7 → diode 13 = spark plug 3 – ground → resistor 8
→Flows through the path of capacitor 7. Other operations are similar to those in the above embodiment.

Alternatively, a high-voltage power distribution method using a power distributor may be used.
This will be explained with reference to the drawings and FIG. Figure 4 shows the generation of a high voltage for ignition with negative polarity. It flows in the path of air gap-center electrode 14a)-secondary winding lb. At this time, the capacitor 7 is charged to the polarity shown. Also, the ion current is the capacitor 7 → → secondary winding 1b → diode 15-h spark plug 3 → earth → resistor 8 → capacitor 7
flows along the route of Other operations are similar to those in the above embodiment. Figure 5 shows a system that generates a positive ignition high voltage. In the figure, the discharge current flows from the secondary winding 1b to the distributor
4 (center electrode 14a → air gap → peripheral electrode] 4b) - Spark plug 3 → ground → diode 10 → capacitor → secondary winding lb.

At this time, the capacitor 7 is charged to the polarity shown.

Further, the ionic current flows through the path of capacitor 7 -> diode 13 -> ignition flag 3 - ground - resistor 8 - capacitor 7. Other operations are similar to those in the above embodiment.

Further, although the above embodiments have shown a configuration in which voltage conversion is performed using a resistor as the ion current detection means, it goes without saying that other configurations may be used.

〔Effect of the invention〕

As described above, according to the present invention, since a capacitor is provided which is charged with a high voltage for ignition and applies a positive bias voltage to the spark plug using this charging voltage, it is not necessary to use a large and expensive C-DC converter. It's not necessary,
A small and inexpensive ion current detection device can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG.
) is a circuit diagram showing the ion current path of the embodiment in FIG.
Figure (b) is a circuit diagram showing the ion current path of the embodiment in Figure 1, Figure 3 is a circuit diagram showing another embodiment of the invention, and Figure 4 is a circuit diagram showing still another embodiment of the invention. FIG. 5 is a circuit diagram showing still another embodiment of the present invention, and FIG. 6 is a circuit diagram showing a conventional device. In the figure, l is an ignition coil, 3 is a spark plug, 7 is a capacitor, 8 is a resistor, and 9 is an output terminal. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Agent Masuo Oiwa Figure 1 Figure 2 (b) Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] An ignition coil that generates a high voltage for ignition of an internal combustion engine; a spark plug to which the high voltage for ignition is applied to the ignition coil and ignites the air-fuel mixture; a spark plug that is charged by the high voltage for ignition; An ion current detection device comprising: a capacitor for applying a positive bias voltage to the capacitor; and a detection means for detecting an ionic current flowing due to the positive bias voltage of the capacitor and ions generated during combustion of the air-fuel mixture.