JP2019105228A - Ignitor of internal combustion engine - Google Patents

Abstract

To suppress a short circuit of spark discharge.SOLUTION: An ignitor 100 of an internal combustion engine predicts an approach of a spark discharge path by detecting the inductance of the spark discharge path, and controls an ignition current so as to expand the spark discharge path when the approach of the spark discharge path is predicted. When the approach of the spark discharge path is predicted, an ignition current is increased. When the approach of the spark discharge path is predicted, electrical energy is supplied to the spark discharge path. By detecting the inductance of the spark discharge path, the approach of the spark discharge path is predicted. A high-frequency superimposition circuit for superimposing and applying a high-frequency signal to the spark discharge path, and a detection circuit for detecting the inductance of the spark discharge path from a phase difference between a voltage and a current of the high-frequency signal are arranged. The high-frequency signal is formed by repeating a pulse signal. The high-frequency signal is a random signal.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ignition system for an internal combustion engine.

  An ignition device for an internal combustion engine, wherein the secondary current (discharge current) of the ignition circuit is made into a rectangular shape with a small time change, thereby causing blowout of the spark discharge path and occurrence of redischarge and loss of ignition energy associated therewith. Patent Document 1 discloses a technique for suppressing Further, there is disclosed a technique for improving the efficiency by feeding back the secondary voltage and secondary current of the ignition circuit to the primary circuit (Patent Documents 2 and 3).

  Also, an ignition device is disclosed that causes the spark discharge to fly to the surrounding space by applying Lorentz force to the spark discharge path by the magnetic field formed by the ignition current (Patent Document 4).

JP 2014-206068 A JP, 2015-63931, A JP, 2015-200284, A International Patent Publication WO 91/15677 Brochure

  By the way, as shown in FIGS. 7A to 7D, the spark discharge path formed between the electrodes of the spark plug extends in the downstream direction by the air flow in the engine cylinder. The elongation increases with time. On the other hand, the air flow in the engine cylinder is disturbed, and its direction and speed fluctuate. Therefore, in the extension process of the discharge path, as shown in FIG. 7E, a short circuit phenomenon occurs due to proximity and contact of the discharge path. When a short circuit occurs in the discharge path, the discharge path length is rapidly shortened, so that the effect of heating the mixture around it is significantly reduced. As a result, the growth of the initial flame is suppressed, leading to a reduction in the rate of heat generation and a misfire.

  There is no known method for detecting the proximity of the spark discharge path or a technique for suppressing the short circuit of the spark discharge from the detected result.

  An embodiment of the present invention predicts proximity of a spark discharge path, and performs control to widen the spark discharge path when proximity of the spark discharge path is predicted. It is.

  Here, when proximity of the spark discharge path is predicted, it is preferable to increase the ignition current to repel the discharge path by Lorentz force in order to suppress a short circuit, and supply electrical energy to the spark discharge path. Is preferred.

  Preferably, the proximity of the spark discharge path is predicted by detecting the inductance of the spark discharge path.

  Further, it is preferable to include a high frequency superposition circuit which superimposes and applies a high frequency signal to the spark discharge path, and a detection circuit which detects an inductance of the spark discharge path from a phase difference between voltage and current of the high frequency signal. .

  Preferably, the high frequency signal is a repetition of a pulse signal. Preferably, the high frequency signal is a random signal.

  According to the present invention, the proximity of the spark discharge path can be predicted, and the short circuit of the spark discharge can be suppressed.

It is a figure showing the composition of the ignition device of the internal-combustion engine in an embodiment of the invention. It is a figure which shows the principle of the detection method of the inductance in embodiment of this invention. It is a figure explaining the shape of a spark-discharge path, and the relation of inductance. It is a figure explaining application and superposition of a signal for detection of an inductance in an embodiment of the invention. It is a figure explaining control of the ignition current in an embodiment of the present invention. It is a figure explaining suppression of the Lorentz force which acts on the spark-discharge path in embodiment of this invention, and the short circuit of a spark-discharge path. It is a figure for demonstrating the subject in the conventional ignition device of an internal combustion engine.

<Basic configuration>
As shown in FIG. 1, an ignition device 100 for an internal combustion engine according to an embodiment of the present invention includes a main circuit 102, an inductance detection circuit 104, an auxiliary current supply circuit 106, and an engine control device 108.

  The main circuit 102 is a circuit provided to supply electric energy to a spark plug provided in the internal combustion engine to ignite the fuel. The ignition coil A2 has a configuration in which a primary coil and a secondary coil having a larger number of turns than the primary coil are electromagnetically coupled. One end of the primary coil is connected to one end of the battery A1 and the secondary coil, and the other end is grounded via the switch A3. The other end of the secondary coil is connected to the center electrode of the spark plug A4.

  In the main circuit 102, prior to the desired ignition start timing, the switch A3 is turned on, and current is supplied from the battery A1 to the ignition coil A2 to store electric energy in the ignition coil A2. At the desired ignition start timing, the switch A3 is turned off to release the electrical energy stored in the ignition coil A2 toward the spark plug A4. As a result, spark discharge is formed between the electrodes of the spark plug A4. The switch A3 is switched in response to a signal from the engine control unit 108.

  In the present embodiment, the main circuit 102 has a simple configuration including a battery A1, an ignition coil A2, and a switch A3. The main circuit 102 may be configured as shown in JP-A-2014-206068 or JP-A-2007-211631. Furthermore, the configuration is not limited to these cases, as long as the function is satisfied.

<Detection of inductance>
As shown in FIG. 2, when a sine voltage E alternating at an angular velocity ω is applied to an electric circuit having a resistance R and an inductance L, the current I flowing through the circuit causes a phase delay θ with respect to the voltage E. The phase delay θ is a function of the inductance L, and as the inductance L increases, the phase delay θ also increases.

  The inductance detection circuit 104 includes a high frequency superposition circuit that applies and superimposes an alternating voltage signal E, which is a weak high frequency signal, to the spark discharge path. The inductance detection circuit 104 superimposes a weak alternating voltage signal E on the spark discharge path, and detects the inductance L of the spark discharge path from the phase delay θ of the signal current I. As shown in FIG. 3, when the spark discharge path is close to a circular shape, the inductance L is large, and in the flat shape, the inductance L is small. Since the spark discharge path is likely to be short-circuited in the flat discharge path, the short circuit of the discharge path can be predicted from the size of the inductance L.

  The inductance detection circuit 104 is added to the main circuit 102. The inductance detection circuit 104 generates a sine voltage signal B1 of the angular velocity ω in synchronization with the discharge start of the spark plug A4. As shown in FIG. 4, the voltage signal B1 applies / superposes the voltage signal B1 on the spark discharge path via the filter B2 (band pass filter or high pass filter). Then, by measuring the terminal voltage of the resistor B3, the inductance detection circuit 104 measures the phase delay θ of the signal current, and detects the inductance L which changes in accordance with the shape of the spark discharge path.

  The detection of the inductance L by the inductance detection circuit 104 is preferably started after the end of the capacity discharge period ts. The capacity discharge period is a period in which spark discharge is performed by the release of electrostatic energy, and the duration is, for example, a period of about 0.02 ms from the discharge start time. In the capacitive discharge period, since the spark discharge path does not extend, the inductance L in that period decreases.

  Further, in the determination of the proximity of the spark discharge path, a pulse voltage may be repeatedly applied in place of the sine wave voltage E, and the phase delay of the current I may be measured. Also, instead of the sine wave voltage E, a voltage that increases or decreases in proportion to the passage of time may be repeatedly applied to measure the phase delay of the current I.

Furthermore, instead of the sine wave voltage E, a random signal voltage E represented by white noise may be applied to measure the phase delay of the current I. In this case, the phase difference can be calculated using the Fourier transform expressed by the following equation.
Here, Z (t) is the impedance in the time domain, which is obtained by dividing the voltage history E (t) in the time domain by the current history I (t) in the time domain. By Fourier transforming this, the absolute value Z (f) of the impedance in the frequency domain and the phase (2πft + θ) of the impedance in the frequency domain can be calculated. Thereby, the phase difference θ between the signal voltage E and the current I can be obtained.

<Control of ignition current>
As shown in FIG. 5A, when the inductance L detected by the inductance detection circuit 104 falls below a predetermined threshold Ll, it can be expected that the spark discharge paths are close. Therefore, as shown in FIG. 5B, the auxiliary current supply circuit 106 supplies an auxiliary current to the spark discharge path when the proximity of the spark discharge path is expected. As a result, as shown in FIG. 6, the Lorentz force F acts on the adjacent discharge paths in the direction in which the two repel each other, the spark discharge paths repel each other, and the short circuit is suppressed. Further, the resistance of the discharge path is lowered due to the increase of the discharge current, so that the potential difference between both of the adjacent discharge paths is lowered, so that the short circuit hardly occurs.

  The auxiliary current supply circuit 106 is a circuit that supplies an auxiliary current to the spark discharge path. An auxiliary current supply circuit 106 is added to the main circuit 102 to supply an auxiliary current to the spark discharge path.

  The auxiliary current supply circuit 106 boosts the voltage of the battery A1 and stores it in the energy input capacitor C1, and the electric energy stored in the energy input capacitor C1 is used as a primary coil of the ignition coil A2 of the main circuit 102. And input energy control means for supplying to the middle tap of The booster circuit is stored in the choke coil C2 by the choke coil C2 having one end connected to the battery A1, the boost switching element C3 for interrupting the conduction state of the choke coil C2, and the on / off operation of the boost switching element C3. The capacitor C1 includes an energy input capacitor C1 for charging the electric energy, and a diode C4 for preventing the electric energy stored in the energy input capacitor C1 from flowing back to the choke coil C2. In the auxiliary current supply circuit 106, electric energy is accumulated in the energy input capacitor C1 by periodically turning on / off the step-up switching element C3.

  The input energy control means includes an energy input switching element C5 for inputting the electric energy stored in the energy input capacitor C1 into the primary coil of the ignition coil A2 of the main circuit 102, and a reverse current of the input energy. It includes a diode C6.

  The auxiliary current supply circuit 106 turns on the switching element C5 for energy injection at time tl when the inductance L detected by the inductance detection circuit 104 falls below the threshold L1, to the ignition plug A4 included in the main circuit 102. Supply auxiliary current. As a result, the auxiliary current is superimposed on the spark discharge path, and the Lorentz force F in the direction in which both repel each other acts between the discharge paths close to each other, and the short circuit is suppressed.

  In the auxiliary current supply circuit 106, the choke coil C2 and the energy input capacitor C1 may not be provided, and the current of the battery A1 may be directly controlled by the energy input switching element C5. Further, instead of the choke coil C2 of the auxiliary current supply circuit 106, an ignition coil A2 may be used in combination. Also, the function of the auxiliary current supply circuit 106 may be provided on the secondary side (high voltage side) of the ignition coil A2.

  The auxiliary current supply circuit 106 may use the control circuit disclosed in Japanese Patent Application Laid-Open No. 2007-211631 or a part thereof.

  Further, in determining the proximity of the spark discharge path, instead of the inductance L, the phase delay θ may be used as an index of the auxiliary current supply start. That is, when the phase delay θ falls below the predetermined threshold θ1, it can be predicted that the spark discharge paths are in close proximity. Therefore, the auxiliary current supply circuit 106 may supply the auxiliary current to the spark discharge path when the proximity of the spark discharge path is predicted based on the value of the phase delay θ.

  Further, the length of the spark discharge path can be estimated by calculating the electrical resistance of the discharge path from the ignition voltage and the ignition current. Therefore, in the determination of the proximity of the spark discharge path, instead of the inductance L, the inductance L 'per unit length of the spark discharge path may be used as an index of the auxiliary current supply start. In the auxiliary current supply circuit 106, the auxiliary current may be supplied to the spark discharge path when the proximity of the spark discharge path is predicted based on the value of the inductance L 'per unit length of the spark discharge path.

  Also, the discharge voltage changes with the change of the length of the spark discharge path. Therefore, in determining the proximity of the spark discharge path, instead of the inductance L, the discharge path length is estimated from the discharge voltage, and the inductance L ′ ′ per unit length of the spark discharge path obtained based thereon is used as an auxiliary current It may be used as an indicator of supply start. In the auxiliary current supply circuit 106, the auxiliary current may be supplied to the spark discharge path when the proximity of the spark discharge path is expected based on the value of the inductance L ′ ′ per unit length of the spark discharge path. .

DESCRIPTION OF SYMBOLS 100 ignition device, 102 main circuit, 104 inductance detection circuit, 106 auxiliary current supply circuit, 108 engine control device, A1 battery, A2 ignition coil, A3 switch, A4 ignition plug, B1 voltage signal, B2 filter, B3 resistance, C1 energy Capacitor for closing, C2 choke coil, C3 boost switching device, C4 diode, C5 energy switching switch, C6 diode.

Claims (7)

  An ignition system for an internal combustion engine, which predicts the proximity of a spark discharge path and performs control so as to widen the spark discharge path when the proximity of the spark discharge path is predicted. An ignition device for an internal combustion engine according to claim 1,
An ignition system for an internal combustion engine, comprising: increasing ignition current when proximity of the spark discharge path is predicted. An ignition device for an internal combustion engine according to claim 1,
An ignition device for an internal combustion engine, comprising: supplying electric energy to the spark discharge path when proximity of the spark discharge path is predicted. An ignition device for an internal combustion engine according to any one of claims 1 to 3, wherein
An ignition system for an internal combustion engine, wherein an approach of the spark discharge path is predicted by detecting an inductance of the spark discharge path. An ignition device for an internal combustion engine according to claim 4.
A high frequency superposition circuit which superimposes and applies a high frequency signal to the spark discharge path;
A detection circuit for detecting an inductance of the spark discharge path from a phase difference between a voltage and a current of the high frequency signal;
An igniter for an internal combustion engine, comprising: An ignition device for an internal combustion engine according to claim 5,
An ignition device for an internal combustion engine, wherein the high frequency signal is a repetition of a pulse signal. An ignition device for an internal combustion engine according to claim 5,
The igniter for an internal combustion engine, wherein the high frequency signal is a random signal.