JP2001073919A - Combustion state detector for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a reverse flow of an electric charged in a capacitor, secure bias voltage required for detecting an ionic current, and perform excellent and stable detection of the ionic current. SOLUTION: A combustion state detector for an internal combustion engine generates bias voltage by charging a capacitor 13 with a primary voltage generated in a primary coil 2a of an ignition coil 2 of the internal combustion engine, applies the bias voltage on spark plugs 14a, 14b arranged in a combustion chamber, and detects an electric current passing from the capacitor 13 to the spark plugs 14a, 14b by an ion generated in the combustion chamber at the time of burning of the internal combustion engine as an ion current. In this combustion state detector for the internal combustion engine, a rectifying element 17 rectifying an electric current passing from the primary coil 2a to the capacitor 13 has a recovery time, from sending the electric current from the primary coil 2a to the capacitor 13 till preventing an electric current passing in the reverse direction, which is not more than 2 μS.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion state detection for an internal combustion engine, which detects a combustion state of the internal combustion engine by detecting, as an ion current, ions generated when an air-fuel mixture burns in a combustion chamber of the internal combustion engine. It concerns the device.

[0002]

2. Description of the Related Art FIG. 7 is a circuit diagram showing a conventional combustion state detecting device for an internal combustion engine. FIG. 8 is a timing chart showing the operation waveform of each part of the circuit of FIG. One end of the primary coil 2a of the ignition coil 2 is connected to the battery 1, and the other end is connected to a switching element 6 for energizing / cutting off the current of the primary coil 2a.

The crank angle sensor 3 detects a crank angle of the internal combustion engine and outputs a signal. The ECU 5 calculates the ignition timing from the signal of the crank angle sensor 3 and the signals of the other various sensors 4 and outputs a signal for driving the switching element 6.

The switching element 6 is driven based on the drive signal of the ECU 5, and the primary coil 2a of the ignition coil 2 is driven.
Current is turned on / off. When the current of the primary coil 2a is cut off, a voltage of several hundred volts is generated at the terminal of the primary coil 2a connected to the switching element 6. This voltage causes a high voltage of several tens of kilovolts to be generated in the secondary coil 2b of the ignition coil 2 and discharges to be generated in the ignition plugs 14a and 14b connected to the secondary coil 2b. To burn.

The voltage of several hundred volts generated in the primary coil 2a causes a current to flow through the path of the rectifying element 7, the current limiting element 8, the capacitor 13, the rectifying element 12,
To charge. The rectifying element 7 prevents the charge stored in the capacitor 13 from flowing backward when the primary coil 2a side falls below a predetermined voltage. Voltage limiting element 11
Restricts the charging voltage of the capacitor 13.

[0006] The voltage charged in the capacitor 13 passes through the current limiting element 10 and the rectifying element 9 and passes through the spark plug 14b.
And the ignition plug 14a via the secondary coil 2b.
To apply an ion current.

The ion current is supplied to a current-voltage conversion circuit 1
5, the voltage is converted into a voltage value, and the ion current signal processing circuit 1
The ECU 6 converts the signal into a combustion state signal indicating the combustion state.
To output the combustion state signal. The ECU 5 determines the combustion state based on the combustion state signal, and reflects the result in ignition timing control and fuel injection control.

[0008]

Generally, a rectifying element that restricts the flow of current in one direction flows a current from the anode side to the cathode side and then flows in the opposite direction for a short time.

In the above-described conventional device, the rectifying element 7 in the path for charging the bias voltage has a slow recovery time until the backflow is prevented. Therefore, as shown by Vbias in FIG.
The voltage charged in 3 drops by a predetermined amount due to the reverse current after the peak.

[0010] Then, the capacitor 13 is not sufficiently charged with the bias voltage necessary for detecting the ionic current, so that the ionic current cannot be detected satisfactorily and it is difficult to accurately determine the combustion state. There was such a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and prevents a charge charged in a capacitor from flowing backward, and secures a bias voltage necessary for detecting an ion current. It is an object of the present invention to provide a combustion state detection device for an internal combustion engine that can perform good and stable ion current detection and can accurately determine a combustion state.

[0012]

A combustion state detecting device for an internal combustion engine according to the present invention generates a bias voltage by charging a capacitor with a primary voltage generated by a primary coil of an ignition coil of the internal combustion engine, and generates the bias voltage. In a combustion state detection device for an internal combustion engine, which is applied to a spark plug disposed in a combustion chamber and detects a current flowing from the capacitor to the ignition plug as an ion current due to ions generated in the combustion chamber during combustion of the internal combustion engine, the primary coil The rectifying element for rectifying the current flowing through the capacitor is a rectifying element having a recovery time of 2 μS or less, which is a time required to prevent the current flowing in the reverse direction after the current flows from the primary coil to the capacitor.

Further, a second rectifying element for reducing the leakage current leaking from the capacitor to the primary coil side to 10 μA or less is provided in the first rectifying element, which is a rectifying element having a recovery time of 2 μS or less, in the same manner as the first rectifying element. Directionally connected to the series.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a circuit diagram showing a combustion state detecting device for an internal combustion engine according to the present invention. FIG. 2 is a timing chart showing operation waveforms of each part of the circuit of FIG. Reference numerals 1 to 6 and 8 to 16 in the figure are the same as those of the conventional device shown in FIG. That is, one end of the primary coil 2a of the ignition coil 2 is connected to the battery 1,
The other end is connected to a switching element 6 for energizing / disconnecting the current of the primary coil 2a.

The crank angle sensor 3 detects a crank angle of the internal combustion engine and outputs a signal. The ECU 5 calculates the ignition timing from the signal of the crank angle sensor 3 and the signals of the other various sensors 4 and outputs a signal for driving the switching element 6.

The switching element 6 is driven based on the drive signal of the ECU 5 and the primary coil 2a of the ignition coil 2 is driven.
Current is turned on / off. When the current of the primary coil 2a is cut off, a voltage of several hundred volts is generated at the terminal of the primary coil 2a connected to the switching element 6. This voltage causes a high voltage of several tens of kilovolts to be generated in the secondary coil 2b of the ignition coil 2 and discharges to be generated in the ignition plugs 14a and 14b connected to the secondary coil 2b. To burn.

The rectifier 17 is a rectifier having a recovery time of 2 μS or less. The voltage of several hundred volts generated in the primary coil 2a flows through the path of the rectifying element 17 → current limiting element 8 → capacitor 13 → rectifying element 12
To charge. The voltage limiting element 11 includes the capacitor 1
3 limit charging voltage.

The voltage charged in the capacitor 13 is passed through the current limiting element 10 and the rectifying element 9 to the ignition plug 14b.
To the ignition plug 14a through the secondary coil 2b, and an ionic current flows.

This ion current is supplied to the current-voltage conversion circuit 1
5, the voltage is converted into a voltage value, and the ion current signal processing circuit 1
The ECU 6 converts the signal into a combustion state signal indicating the combustion state.
To output the combustion state signal. The ECU 5 determines the combustion state based on the combustion state signal, and reflects the result in ignition timing control and fuel injection control.

In this embodiment, the rectifying element 17
Uses an element having a recovery time of 2 μS or less, so that the time required for the charge charged in the capacitor 13 to flow back through the rectifying element 17 becomes very short, and as shown by Vbias in FIG. The voltage hardly drops.

The following is the recovery time of the rectifier and the capacitor 1
3 is experimental data showing the relationship between the charging voltages for charging 3;

Recovery time Charge voltage 0.1 μS 140 V 2 μS 130 V 10 μS 105 V

In order to detect the ion current satisfactorily, a charging voltage of usually 130 V or more is required. Therefore, in order to prevent the charging voltage from lowering, it is necessary to use an element having a recovery time of 2 μS or less.

In the combustion state detecting device for an internal combustion engine having such a configuration, the rectifying element 17 in the path for charging the bias voltage is an element having a fast recovery time, so that the charge stored in the capacitor 13 flows back. To prevent Therefore, a bias voltage necessary for detecting the ion current can be secured, and good and stable ion current detection can be performed, and accurate determination of the combustion state can be performed.

Embodiment 2 In the first embodiment, a rectifier having a fast recovery time is used. However, when a rectifier having a fast recovery time is used, a leak current when a reverse bias is applied tends to increase. For example, in the case of a rectifying element such as a diode, a heavy metal (such as gold / platinum) is deposited on silicon, heat-treated, and diffused to shorten the recovery time. And since heavy metals are included, the leakage current becomes large at high temperatures.

FIG. 3 is a diagram showing the path of the leak current. FIG. 4 is a timing chart showing how a leak current is generated. The leakage current flows through the path of the capacitor 13, the current limiting element 8, the rectifying element 17, the primary coil 2a, the battery 1, and the current-voltage conversion circuit 15, as indicated by arrows in FIG.

The ions generated during combustion of the internal combustion engine are 13
When a bias voltage of about 0 V is applied, an ion current of several tens of μA flows when the combustion is normal. However, when the leakage current of the rectifying element 17 is several tens μA, the waveform of the ion current becomes small, and it becomes difficult to identify the ion current (FIG. 4).

The present embodiment aims at preventing a leak current due to such a reverse bias. FIG.
FIG. 3 is a circuit configuration diagram showing another example of the combustion state detecting device for an internal combustion engine of the present invention. FIG. 6 is a timing chart showing the operation waveform of each part of the circuit of FIG. 5, reference numerals 1 to 6 and 8 to 17 are the same as those in the first embodiment shown in FIG. That is, the rectifier 17 has a recovery time of 2
It is an element of μS or less. The rectifier 17 is a capacitor 1
3 prevents the charge charged in 3 from flowing back.

In the present embodiment, the rectifying element 27 is connected to the rectifying element 17 in series. Rectifier 27
Has a leakage current of 10 μA for a steady reverse bias.
The following rectifier elements are provided. Generally, when the ionic current is the smallest, such as when the internal combustion engine is started, the ionic current becomes 1
Since it is about 0 μA, if the leak current is 10 μA or less, it is not difficult to identify the ion current.

In the combustion state detecting device for an internal combustion engine having such a configuration, the rectifying element 17 having a fast recovery time and the rectifying element 27 having a small leak current are connected in series, so that the charging voltage immediately after charging is reduced. It is possible to achieve both prevention and prevention of leakage current with respect to a steady reverse bias, perform good and stable ion current detection, and accurately determine the combustion state.

[0031]

The combustion state detecting device for an internal combustion engine according to the present invention charges a capacitor with a primary voltage generated by a primary coil of an ignition coil of the internal combustion engine to generate a bias voltage, and distributes the bias voltage in a combustion chamber. A current flowing from a primary coil to a capacitor in a combustion state detection device for an internal combustion engine which detects a current flowing from a capacitor to a spark plug as an ion current due to ions generated in a combustion chamber during combustion of the internal combustion engine by being applied to a provided spark plug. Is a rectifying element having a recovery time of 2 μS or less, which is a time required for the rectifying element for rectifying the current to prevent the current flowing in the reverse direction after the current flows from the primary coil to the capacitor. for that reason,
Prevents the charge stored in the capacitor from flowing back,
A bias voltage necessary for detecting an ion current can be secured, a good and stable ion current can be detected, and an accurate determination of a combustion state can be performed.

Further, the first rectifier, which is a rectifier having a recovery time of 2 μS or less, is provided with a second rectifier for reducing the leak current leaking from the capacitor to the primary coil to 10 μA or less, as in the first rectifier. Directionally connected to the series. Therefore, it is possible to prevent a drop in the charging voltage immediately after charging and to prevent a leakage current with respect to a steady reverse bias, to perform good and stable ion current detection, and to accurately determine a combustion state. Become.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a combustion state detecting device for an internal combustion engine according to the present invention.

FIG. 2 is a timing chart showing operation waveforms of each part of the circuit.

FIG. 3 is a diagram showing a path of a leakage current.

FIG. 4 is a timing chart showing a state in which a leak current is generated.

FIG. 5 is a circuit configuration diagram showing another example of the combustion state detecting device for an internal combustion engine of the present invention.

6 is a timing chart showing operation waveforms of respective parts of the circuit of FIG.

FIG. 7 is a circuit configuration diagram showing a conventional combustion state detection device for an internal combustion engine.

8 is a timing chart showing operation waveforms of each part of the circuit of FIG.

[Explanation of symbols]

2 ignition coil, 2a primary coil, 13 capacitor, 14a, 14b spark plug, 17 recovery time 2μ
S rectifier element of S or less, 27 Rectifier element with leak current of 10 μA or less.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shimizu Murata 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsui Electric Co., Ltd. (72) Inventor Mitsuru Koiwa 2-3-2 Marunouchi, Chiyoda-ku, Tokyo F term in Mitsubishi Electric Corporation (reference) 3G019 AB01 AB02 AB03 CD06 FA02 FA05 LA05 3G084 BA13 BA15 BA16 DA04 FA19

Claims (2)

[Claims] A capacitor is charged with a primary voltage generated by a primary coil of an ignition coil of an internal combustion engine to generate a bias voltage, and the bias voltage is applied to a spark plug disposed in a combustion chamber, and the bias voltage is applied to the ignition plug. In a combustion state detection device for an internal combustion engine that detects a current flowing from the capacitor to the ignition plug by ions generated in the combustion chamber at the time of combustion as an ion current, a rectifying element that rectifies a current flowing from the primary coil to the capacitor, A combustion state detecting device for an internal combustion engine, wherein the rectifying element has a recovery time of 2 μS or less, which is a time required to prevent a current flowing in the reverse direction after a current flows from the primary coil to the capacitor. 2. A second rectifying element, which is a rectifying element having a recovery time of 2 μS or less, having a leakage current leaking from the capacitor to the primary coil side of 10 μA or less.
The combustion state detecting device for an internal combustion engine according to claim 1, wherein the rectifying elements are connected in series in the same direction as the first rectifying element.