JPH04179864A - Ion current detector - Google Patents

Abstract

PURPOSE:To improve detectability by applying positive-polarity bias voltage to a pair of spark plugs, respectively. CONSTITUTION:At a spark timing for an internal combustion engine, ignition high voltage arises in the secondary winding 1b of an ignition coil 1, a discharge current flows in a passage shown in an arrow mark, and discharge occurs between the respective electrodes of spark plug 3a, 3b to ignite and fire mixture in a cylinder in a compression stroke. At this time, the combustion of mixture involves electrolytic dissociation to create ions. With the movement of electrons due to positive-polarity bias from a power source 8, an ion current flows in a cylinder where combustion occurs, but electrons have greatly smaller mass and faster moving speed than positive ions so that a great amount of ion current is obtained. Voltage developed in an output terminal 10 by the ion current can be detected to identify the combustion of mixture. It is thus possible to improve detectability.

Description

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

[Conventional technology]

A conventionally known device of this kind will be explained with reference to FIG. In the figure, 1 is the primary winding 1a and the secondary winding l
2 is a power transistor connected to the primary winding 1a to intermittent the primary current; 3a is connected to the positive polarity side of the secondary winding lb, and is installed in a first cylinder of an internal combustion engine (not shown). 3b is the secondary winding lb
A spark plug 4 is connected to the negative polarity side of the secondary winding lb and is provided in the 20th cylinder of the internal combustion engine (not shown), and is connected to the negative polarity side of the secondary winding lb, and applies a negative bias voltage to the spark plug 3a3b. 5 is a resistor connected in series with the power supply 4 and converts the ionic current into voltage; 6 is an output terminal for detecting the voltage generated in the resistor 5; Together, they constitute ion current detection means. A diode 7 is interposed between the power source 4 and the secondary winding lb to block reverse current.

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 negative winding 1a is cut off, a high voltage for ignition is generated in the secondary winding lb. A discharge is generated between each electrode of the spark plaque 3a3b. Here, the ignition timing is set so that one of the first and 20th cylinders is in the compression stroke and the other is in the exhaust stroke.

Therefore, at the ignition timing, either a discharge occurs in both the spark plugs 3a3b, or the air-fuel mixture is ignited and combusted only in the cylinder in the compression stroke. This is the so-called simultaneous ignition method.

At this time, ionization occurs as the mixture burns, and ions are generated. Here, the electrode of the spark plug 3a3b acts as an electrode for detecting ion current after the above-mentioned discharge, and an ion current flows due to the movement of positive ions due to the negative 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]

Conventional ion current detection devices are configured to generate ion current with negative polarity bias, so the amount of ion current is determined by the amount of movement of cations, or because cations have large mass and movement speed is slow. However, the amount of ion current was also very small, which caused the problem of low detectability.

This invention was made to solve the above-mentioned problems, and an object thereof is to obtain an ion current detection device that can obtain a large amount of ion current and has excellent detectability.

[Means to solve the problem]

The ion current detection device according to the present invention is provided with bias means for applying a positive polarity bias voltage to each of a pair of spark plugs.

[Function]' The biasing means in the present invention applies a bias voltage of positive polarity to each of the pair of spark plugs to generate an ionic current by movement of electrons.

[Embodiment of the Invention] An embodiment of the invention will be described below with reference to FIGS. 1 and 2. In the figure, 8 is a power supply connected to the positive polarity side of the secondary winding lb and is a bias means for applying a positive bias voltage to the spark plug 3a3b, and 9 is a power supply 8
A resistor 10 is connected in series with the resistor 9 to convert the ionic current into voltage, and is an output terminal for detecting the voltage generated in the resistor 9, and together with the resistor 9 constitutes an ionic current detecting means. A diode 11 is interposed between the power supply 8 and the secondary winding lb to block reverse current.

In the structure as described above, a high voltage for ignition (approximately 10 to 25 K) is applied to the secondary winding lb at the ignition timing of the internal combustion engine.
V) is generated, and a discharge current flows in the path shown by the arrow in FIG. 2(a), generating a discharge between each electrode of the spark plug 3a3b, thereby igniting and burning the air-fuel mixture in the cylinder in the compression stroke.

At this time, as in the conventional device, ionization occurs as the air-fuel mixture burns, and ions are generated. Here, due to the movement of electrons due to the positive polarity bias (approximately 300 V) of the power supply 8,
An ion current flows in the path shown by the arrow in Figure 2(b) in the cylinder where combustion occurred, but since electrons have a significantly smaller mass than cations and move faster, the amount of ion current is also large ( (approximately 10 to 50 times larger than conventional devices). Combustion of the air-fuel mixture can be confirmed by detecting the voltage generated at the output terminal 10 due to the generation of this ion current.

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

〔Effect of the invention〕

As described above, according to the present invention, a positive bias voltage is applied to each of a pair of spark plugs, and an ionic current is generated by the movement of electrons, so a large amount of ionic current can be obtained. Therefore, an ion current detection device with excellent detectability can be obtained.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG.
) is a circuit diagram showing the discharge path of the embodiment in FIG. 1, and FIG.
) is a circuit diagram showing the ion current path of the embodiment in FIG.
The figure is a circuit diagram showing a conventional device. In the figure, l is the ignition coil, lb is the secondary winding, 3a3
b is a spark plug, 8 is a power supply, 9 is a resistor, 10 is an output terminal, and 11 is a diode. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Agent: Masuo Oiwa Seki 1, Figure 2

Claims (1)

[Claims] An ignition coil that generates a high voltage for ignition, a pair of spark plugs connected to both ends of the ignition coil secondary winding, and a pair of spark plugs connected to one end of the positive polarity side of the ignition coil secondary winding via a rectifier, Bias means for applying a positive bias voltage to each of the pair of spark plugs, and detection means for detecting an ion current flowing due to the positive bias voltage of the bias means and ions generated during combustion of the air-fuel mixture. Equipped with an ion current detection device.