JP3347007B2 - Ignition device for internal combustion engine provided with ion current detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to an internal combustion engine for a vehicle, which is provided with an ion current detecting device capable of applying a voltage to a spark plug to flow an ion current when an air-fuel mixture is burning. The present invention relates to an ignition device for an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, in a vehicle engine, a lean burn control (hereinafter, referred to as a lean burn control) for controlling an operation by setting an air-fuel ratio higher than a stoichiometric air-fuel ratio in order to improve fuel efficiency and reduce emissions. (For example, JP-A-6-34491). In such lean burn control, for example, an ion current is passed through the combustion chamber,
In some cases, the ion current is detected to detect combustion fluctuation, and feedback control is performed in lean burn control.
In this case, in order to detect the ion current, an ion current detection device that applies a detection voltage to the plug gap of the spark plug is connected to the secondary coil of the ignition coil of the ignition device.

In an ignition device having such an ion current detecting device, an ion current is generated by applying a detection voltage to the plug gap after the discharge is completed in the plug gap by an ignition signal. . Normally, this ion current is weak, and when knocking occurs, a current corresponding to the knock frequency is superimposed. Therefore, knock control such as detecting the knock frequency component and adjusting the ignition timing is performed. Thus, it is possible to control the combustion state to be more stable according to the operating conditions.

[0004]

By the way, for example, as shown in FIG. 8 (a), an ion current detecting device 91 is connected to a low voltage side of a secondary coil 92c of an ignition coil 92. , The ignition device 200 has a stray capacitance 9 from the secondary coil 92 c to the spark plug 93.
4 and by considering the combustion resistor 95 of the spark plug 93, a low pass filter and the equivalent configuration shown in FIG. 8 (b) (in the figure, R _92, the secondary side coil 92
96 is a switching transistor for the resistance of c). For this reason, when the ion current flows after ignition, the region where the frequency of the ion current is high is filtered and attenuated gently. In this case, the frequency characteristics of the equivalent low-pass filter, specifically, the cutoff frequency may be substantially equal to or lower than the frequency of the knock frequency component fnc.

Therefore, even if knocking occurs and knock frequency component fnc is superimposed on ion current, as shown in FIG.
Is very low, or the cut-off frequency is higher than the cutoff frequency despite the fact that they are superimposed, so that the knock frequency component fnc may not be detected. Therefore, knocking cannot be properly detected, and knock control may not be performed accurately.

An object of the present invention is to solve such a problem.

[0007]

In order to achieve the above object, the present invention takes the following measures. That is, the ignition device of the internal combustion engine provided with the ion current detection device according to the present invention is characterized in that the means for changing the frequency characteristic of a circuit centering on the ignition coil is connected in parallel to the primary coil of the ignition coil, In this configuration, the ion current is suppressed from attenuating in the frequency band of the frequency component. With such a configuration, even if the basic configuration of the ignition device has characteristics equivalent to a low-pass filter, it is possible to detect a knock frequency component before the ion current detected by the ion current detection device attenuates. Therefore, occurrence of knocking can be reliably detected, and knock control with high accuracy can be performed.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ignition coil for applying a discharge voltage to a spark plug connected to a secondary coil by generating a spark in a plug gap by interrupting a current to a primary coil. An ion current detection device that applies an ion current detection voltage to the spark plug through the secondary coil to generate an ion current when the air-fuel mixture burns, and detects the ion current. A change means for changing the impedance of the ignition coil is connected in parallel to the side coil, and the ion on which the knock frequency component is superimposed is connected.
An ignition device for an internal combustion engine including an ion current detection device characterized by detecting a current.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. The ignition device 100 in FIG. 1 is for an internal combustion engine for an automobile, that is, an engine, and shows a configuration for one cylinder in an engine having a plurality of cylinders such as three cylinders. The ignition device 100 of this embodiment is a so-called full-transistor type, and may basically have a configuration known in the art, and includes an ignition coil having a primary coil 1p and a secondary coil 1c. 1 and a switching transistor 2 connected to the low-voltage side terminal of the primary coil 1p of the ignition coil 1. The ignition device 100 of this embodiment includes at least a resistor 3 as a changing unit for changing the characteristics of the primary coil 1p, and is connected in parallel to the primary coil 1p. This resistor 3 has a resistance value of, for example, about 1 Ω or a DC resistance value of the primary coil 1p, and as shown in FIG. This circuit changes the frequency characteristics of a circuit composed of the circuit 5 and the combustion resistor, and changes the cutoff frequency of the circuit to a higher frequency side. A spark plug 4 is connected between the secondary coil 1c and the ground G on the high voltage side.
The illustration of the igniter for driving the switching transistor 2 is omitted.

An ion current detecting device, that is, a charge amplifier 7 is connected to the low voltage side of the secondary coil 1c of the ignition coil 1. When a discharge voltage is generated in the secondary coil 1c, the charge amplifier 7 charges a charge voltage for generating an ion current with the discharge voltage, and when the discharge is completed, the charge voltage is applied to the spark plug 4c.
And amplifies and outputs the weak ion current that flows. The charge amplifier 7 detects the primary current flowing through the primary coil 1p of the ignition coil 1 to detect the end of the discharge, and detects that the primary current has fallen below a preset threshold level after ignition. Built-in current measurement and comparison circuit.
In order to detect knocking, a knock detection device including a band-pass filter that filters only a knock frequency component superimposed on the ion current during knocking may be connected to the charge amplifier 7.

In such a configuration, the switching transistor 2 is turned on by the ignition signal SIg from the igniter, and then turned off, so that a back electromotive voltage is generated in the primary coil 1p, thereby discharging to the secondary coil 1c. Voltage is generated. When this discharge voltage is applied to the spark plug 4, spark discharge occurs in the plug gap of the spark plug 4 and combustion starts. On the other hand, a charge voltage is applied from the charge amplifier 7 to the spark plug 4 at the time when the discharge ends, and an ion current Ii is generated in the combustion chamber (FIG. 3).

The ion current Ii is detected by the charge amplifier 7, amplified and output. This ion current Ii
Includes a wide range of frequencies, but a circuit constituted by the ignition coil 1, the stray capacitance 5, and the combustion resistor 6 acts as a low-pass filter for the ion current Ii. In this circuit, since the resistor 3 is connected to the primary coil 1p of the ignition coil, the impedance of the ignition coil 1 is reduced. As a result, like the equivalent circuit shown in FIG.
The cutoff frequency when considered as a low-pass filter is higher than that when the resistor 3 is not connected in parallel, and the frequency characteristic in which the current value of the ion current Ii slightly increases in the frequency band including the knock frequency component fn. Become. Therefore, when the resistor 3 is not connected in parallel, the knock frequency component fn is substantially equal to the upper limit frequency of the frequency band of the ion current Ii, whereas the knock frequency component fn is lower than the cutoff frequency. Since it belongs to the band, knocking can be detected at a sufficient signal level. In the figure, RL is the resistance of the secondary coil 1c.

The present invention is not limited to the embodiment described above. For example, instead of connecting the resistor 3 to the primary coil 1p of the ignition coil 1, the primary coil 1p may be short-circuited for a predetermined period. Specifically, as shown in FIGS. 5 and 6, a mechanical or semiconductor switch element 1 is attached to the primary coil 1p.
3 is connected in parallel to detect the ion current Ii,
Alternatively, the switch element 13 is operated (turned on) only during a period in which the knock frequency component fn is likely to be superimposed to detect knocking. The detection of the ion current Ii
For example, it may be started from the end of the discharge, and then set to the next rising of the ignition signal or from the end of the discharge to a predetermined crank angle. Further, the period in which knock frequency component fn is likely to be superimposed is generally after the maximum combustion pressure, and thus may be set, for example, from the top dead center to a predetermined crank angle.

As described above, by short-circuiting the primary coil 1p of the ignition coil 1 by the switch element 13, the frequency characteristic as a low-pass filter of the circuit including the ignition device 100 can be changed as in the above-described embodiment. (FIG. 7). In this case, by setting the period in which the switch element 13 is short-circuited as described above, it is possible to avoid adversely affecting the original performance of the ignition coil 1, that is, the performance of applying a sufficient discharge voltage to the spark plug 4. can do.

In addition, the configuration of each part is not limited to the illustrated example, and various modifications can be made without departing from the spirit of the present invention.

[0016]

As described above, according to the present invention, since the changing means for changing the characteristics of the primary coil of the ignition coil is connected in parallel to the primary coil, the frequency band in which the ion current is attenuated is changed. Can be raised. Therefore, when the detected ion current contains a knock frequency component, the problem that the knock frequency component is attenuated and cannot be detected due to the frequency characteristics of the circuit constituting the ignition device can be solved.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram showing one embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram during operation of the embodiment.

FIG. 3 is a waveform chart showing a relationship between an ion current and an ignition signal according to the embodiment.

FIG. 4 is a graph showing a relationship between a frequency band of an ion current and a knock frequency component of the embodiment.

FIG. 5 is an electric circuit diagram showing another embodiment of the present invention.

FIG. 6 is an equivalent circuit diagram at the time of operation of another embodiment.

FIG. 7 is a graph showing a relationship between a frequency band of an ion current and a knock frequency component according to another embodiment.

FIG. 8 is an electric circuit diagram of a conventional example, an equivalent circuit diagram thereof, and a graph showing a relationship between a frequency band of an ionic current and a knock frequency component.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ignition coil 1p ... Primary side coil 1c ... Secondary side coil 3 ... Resistance 7 ... Charge amplifier 13 ... Switch element

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuhiko Okamura 1-115-27 Tsukamoto, Yodogawa-ku, Osaka Die Inside Diamond Electric Co., Ltd. (72) Inventor Yoshiyuki Fukumura 1-15-27 Tsukamoto, Yodogawa-ku, Osaka Die (56) References JP-A-62-48962 (JP, A) JP-A-8-338298 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02P 17 / 12

Claims (2)

(57) [Claims] An ignition coil for applying a discharge voltage to a spark plug connected to a secondary coil by generating a spark in a plug gap by interrupting a current to a primary coil, and when the air-fuel mixture is burned by the spark. An ion current detection device that applies an ion current detection voltage to a spark plug via a secondary coil to generate an ion current and detects the ion current.The primary coil of the ignition coil includes an ignition coil. An ignition device for an internal combustion engine equipped with an ion current detection device, characterized in that a change means for changing the impedance of the internal combustion engine is connected in parallel, and an ion current on which a knock frequency component is superimposed is detected . 2. The method according to claim 1, wherein the changing means detects the ion current during the period.
It is a switch element that short-circuits the primary coil
Internal combustion equipped with the ion current detecting device according to claim 1
Engine ignition device.