JPH04136485A - Detection of combustion state and device therefor in internal combustion engine - Google Patents

Abstract

PURPOSE:To surely detect the ion electric current and surely detect the misfire of an internal combustion engine even by a one-coil one-plug type electric current interruption type ignitor by installing a means for generating the mask voltage for suppressing the electric discharge noise generated in the time band different from the ion electric current because of electric discharge. CONSTITUTION:As for a wave form shaping circuit 10, the polarity of the output (b) of an ion electric current detection circuit which is not shown on the figure is reversed by a reversing circuit 20, and a signal bR is generated. Further, one shot pulses P1 and P2 are generated in the circuits 16 and 17 for masking the noise which is generated in the above-described output (b), and the NOR is taken in a NOR gate 18, and the output is inputted as a mask wave form (c) into an AND gate 19. Further, the above-described signal bR and the threshold level L are compared in a circuit 21, and the logic product with the mask wave form (c) is taken in an AND gate 19, and the wave form shaping output (i) is obtained, having the time band other than the mask time as window. Accordingly, noise can be sorely removed by two masks.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method and device for detecting the combustion state of an internal combustion engine, and particularly to a method and apparatus for detecting the combustion state of an internal combustion engine, and in particular, detects the combustion state by an ionic current flowing through a spark plug immediately after one ignition. The present invention relates to a combustion state detection method and apparatus for an internal combustion engine suitable for use in the following.

[Conventional technology]

Immediately after an electric discharge occurs in a car engine's spark plug, the air in the gap becomes ionized. Therefore,
If a voltage different from that for ignition is applied to the spark plug, an ionic current will flow for a short time after one ignition. The state of this ion current and its generation timing change depending on the combustion state of the engine and the timing of ignition. Therefore, by detecting and measuring the ion current, it is possible to know the combustion state and ignition timing of the engine.

As a conventional technique for detecting the combustion state of an internal combustion engine using such a method, for example, U.S. Patent No. 4,648,367 (M
ar, 10.1987). In this conventional technology, a measuring capacitor is provided in a capacitor discharge type ignition device using a discharging capacitor, this measuring capacitor is also charged in a charging circuit for charging the discharging capacitor, and this charging voltage is applied to the ignition plug. This is used as a current source for the ion current after discharge, and this ion current is measured to detect the combustion state. Another conventional technique, disclosed in Japanese Patent Application Laid-Open No. 63-68774, involves applying a voltage from a separate power supply for detecting ion current to the spark plug, and the ionic current flowing due to this voltage after discharge. is being measured. The above two conventional techniques also take measures to distinguish between the noise component generated by the ignition signal and the like and the ion current.

[Problem to be solved by the invention]

The technique disclosed in the above US patent is directed to a capacitor discharge type ignition device, and this prior art cannot be applied to a primary current interruption type ignition device which has different noise generation characteristics. Also, the piston position signal (crank angle)
The ion current is detected by providing a window for detecting early ignition (time period for detecting ion current) and a window for detecting engine knock.
Other window setting methods are not considered and are not intended for misfire detection.

On the other hand, the prior art disclosed in JP-A No. 63-68774 detects early ignition by creating a window based on the ignition timing, but it also does not take into account various window settings and is not intended to detect misfires. It is not intended to be.

An object of the present invention is to provide a 1-coil, 1-plug type primary current interrupting ignition system for internal combustion engine combustion in which engine misfires are reliably detected by eliminating noise through windows set using various setting methods. The present invention provides a state detection method and device.

[Means to solve the problem]

The above object is achieved by masking the ion current detector output for a predetermined time from the rise of the ignition signal and for a predetermined time from the fall of the ignition signal,
or by masking the ion current detector output for a predetermined period of time from the point at which the ignition spark ceases;
Alternatively, this can be achieved by masking the ion current detector output from the rise of the ignition signal until a predetermined period of time has elapsed from the fall of the ignition signal, or by detecting the ion current while the ignition coil - next side current is flowing. This is accomplished by masking the device output.

[For production]

In a primary current cutoff type ignition system, a large noise is generated when the ignition signal is turned on and at the moment the spark stops, and this is detected by an ion current detector along with the original ion current.

However, the ionic current is generated a little while after the spark plug stops sparking. Therefore, by using any of the methods shown in the above means, both of the above noises or at least the noise generated immediately before the ion current can be reliably masked, and the ion current can be observed accurately.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 5 is a block diagram showing an ignition device and an ion current detection device, in which diodes 4, 6, a capacitor 5, and a resistor 7 constitute an ion current detection circuit 8. The power transistor 1 is activated by the ignition signal a from the control unit 12.
When turned on, current flows through the primary side of the ignition coil 2.

When the primary current is turned off due to the ignition signal being turned off, the ignition coil 2
A flyback voltage is generated on the secondary side of the spark plug 3, and this voltage causes a negative spark to fly to the spark plug 3. Further, the capacitor 5 is charged by the discharge current at that time. The Zener diode 4 limits the charging voltage to the capacitor 5, and the diode 6 and the resistor 7 prevent charging from slowing down.

When the air-fuel mixture is combusted by the spark from the spark plug 3, the gap between the plugs is ionized and conductive, and the energy stored in the capacitor 5 is released and the ionic current 9 flows through the resistor 7.
flows through. Therefore, by measuring the terminal voltage of this resistor 7, the ion current 9 can be detected. The output of the ion current detection circuit 8 is shaped by a waveform shaping circuit IO, which is a feature of this embodiment, and the ion current detection signal is displayed on the display 11. The output i of the waveform shaping circuit 10 is input to the control unit 12, and control is performed according to the output of the ion current. For example, when a phenomenon such as knocking, A/F change, or misfire appears in the ion current, ignition timing control and fuel control are performed by a computing unit inside the control unit 12 in accordance with the phenomenon.

FIGS. 1 and 2 are a functional configuration diagram showing an example of a waveform shaping circuit that is a feature of this embodiment, and a flowchart showing its operation. The polarity of the output of the ion current detection circuit 8 is inverted by the inverting circuit 20, and the signal bR is obtained.

As seen in the waveform, the moment t when the ignition signal a turns on
At the moment t3 when sparks no longer fly between the spark plug and the ignition plug, a large noise is generated in the output of the ion current detection circuit 8.

In order to mask this noise, a one-shot pulse is generated by the one-shot pulse generation circuits 16 and 17 in FIG. 1 using the rising time t1 and falling time t2 of the ignition signal a as triggers, and the exclusive logic sum as N
The OR gate 18 takes the output and inputs it as a mask waveform C to the AND gate 19.

Here, each one-shot pulse PI, P2 (negative pulse)
The width of the one-shot pulse P1 generated in synchronization with the rising edge of the ignition signal a is approximately 1 m, although the width of the one-shot pulse P1 generated in synchronization with the rising edge of the ignition signal a is approximately 1 m.
The width of the other one-shot pulse P2 may be approximately 1 ms to include time t3. and,
A slice circuit 21 slices the output of the ion current detection circuit 8 using a threshold level L that varies depending on various conditions such as engine speed and load, and then performs a logical product with a mask waveform C using an AND gate 19. By taking the time period other than the mask as a window, the ion current i is obtained. In this way, noise is reliably removed by the two masks, and other small noises are also removed by the slice 2o, making it possible to reliably detect the ion current.

3 and 4 are a functional block diagram showing a second embodiment of the waveform shaping circuit 1o and a time chart showing its operation. In this embodiment, a spark signal is taken in instead of an ignition signal, and a one-shot pulse is generated by the pulse generator 22 using the time t3 when there is no spark in the spark plug as a trigger. This pulse P3 is also a negative pulse, and its width is It changes depending on various conditions such as the rotation speed and load, but at time t3
It is sufficient to cover the time when the noise occurs immediately after.

When the detection current bR is masked by this pulse P3, a little noise at t=tl remains in the output i of the AND gate 19 in addition to the ion current. However, since this is temporally separate from the ion current, there is no need to worry about disturbing the measurement.

FIG. 6 is a functional block diagram showing a third embodiment of the waveform shaping circuit 10. In this case, as shown in mask c3 of FIG. is set and reset after a delay τ from the falling point t2, and this RS flip-flop 23
A pulse obtained by inverting the output of is used as a mask. Here, if the delay τ is set to a value that is larger than the time from time t2 to the subsequent occurrence of noise and does not interfere with ion current detection, noise can be removed reliably.

FIG. 7 is a flowchart showing a modification of the third embodiment, in which the waveform shaping circuit is mainly composed of an A/D converter (not shown). This means that when the ignition signal is on and the primary current is not flowing (step 601), the prohibition time τ from the off point (falling edge) t2 is calculated from the engine rotation speed, load, etc. (step 602). Operate the A/D converter only when (steps 603 and 604
). This embodiment is functionally the same as the third embodiment, ie, FIG. 5, and its mask is the same as the mask C3 in FIG. 2, and all noise is removed to obtain the output i4 shown in FIG. 4. . Furthermore, in this embodiment, if step 601 in FIG. 7 is replaced with detection of the point in time when the spark signal is turned off, the present embodiment becomes functionally similar to the second embodiment.

That is, the characteristic is that the left side of the pulse P3 in FIG. 4 is widened, and both noises are removed.

FIG. 8 is a functional block diagram showing a fourth embodiment of the waveform shaping circuit 10, which takes in the emitter voltage of the -order current cutoff power transistor 1 (FIG. 5).

From this voltage, it is detected 23 that the primary current of the ignition coil 3 has completely stopped, and the window is opened.

At this time as well, a waveform shaping circuit output similar to that shown in FIG. 2 is obtained.

〔Effect of the invention〕

According to the present invention, it is possible to reliably detect the ion current that reflects the combustion state of the internal combustion engine even in a one-coil, one-plug type current interrupting ignition device, and in particular, it is possible to reliably detect the presence or absence of a misfire in the internal combustion engine. There is.

[Brief explanation of drawings]

1 and 2 are functional block diagrams showing a first embodiment of a waveform shaping circuit which is a feature of the present invention, and a time chart showing its operation. FIG. 5 is a block diagram of an ignition device and an ion current detection device, and FIGS. 6 and 7 show a third embodiment of a waveform shaping circuit. FIG. 8 is a functional block diagram showing a fourth embodiment of the waveform shaping circuit. 2... Ignition coil, 3... Spark plug, 5... Capacitor, 7... Resistor, 8... Ion current detection circuit, 9... Ion current, 17.18.22... One shot pulse generation, I8...NOR gate, 19...
・AND gate, 21...slice, 23...RS
Flip-flop, 24... - next current complete off detection. Representative Patent Attorney Tadashi Akimoto Actual Figure 2 t2 Square 7 NA Type C3-1-t--j Mihon f7---Figure] (Voluntary) February 6, 1991

Claims (1)

[Claims] 1. A measurement voltage is applied to the spark plug of an ignition device that is configured to ignite using the high voltage generated on the secondary side when the primary current of the ignition coil is cut off, and the ionic current generated after discharge is measured. At the same time as detecting the ion current, a mask voltage is generated to block discharge noise generated by the discharge at a time different from the ion current, and a detection signal of the ion current is not output while the mask voltage is on. A method for detecting a combustion state of an internal combustion engine, characterized in that the discharge noise mixed in the detection signal is removed. 2. The combustion state detection method for an internal combustion engine according to claim 1, wherein the ion current detection signal is sliced by a predetermined threshold value. 3. When the primary current of the ignition coil is cut off, the high voltage generated on the secondary side is used to ignite.A measurement voltage is applied to the spark plug of the ignition device to detect the ionic current generated after discharge, and from the rise of the ignition signal. The detection is performed by generating a mask voltage that is ON only for a first predetermined time and a second predetermined time from the fall of the ignition signal, and not outputting the detection signal of the ion current while the mask voltage is on. A method for detecting a combustion state of an internal combustion engine, characterized by removing the discharge noise mixed into a signal. 4. When the primary current of the ignition coil is interrupted, a measuring voltage is applied to the ignition plug of the ignition device that ignites the secondary side with the high voltage generated, and the ionic current generated after discharge is detected, and the spark of the ignition plug is detected. The discharge noise mixed into the detection signal is removed by generating a mask voltage that remains on for a predetermined period of time from the time when the mask voltage disappears, and not outputting the detection signal of the ion current while the mask voltage is on. A method for detecting the combustion state of an internal combustion engine. 5. Apply measurement voltage to the spark plug of the ignition device, which ignites with the high voltage generated on the secondary side when the primary current of the ignition coil is cut off, and detect the ionic current generated after discharge, and also detect the rising point of the ignition signal. , a mask voltage is generated that remains on until a predetermined time elapses from the falling point, and the detection signal of the ion current is not output while the mask voltage is on, thereby eliminating the discharge noise mixed in the detection signal. A method for detecting a combustion state of an internal combustion engine, characterized in that: 6. Detection means for detecting the ionic current generated after discharge by applying a measurement voltage to the spark plug of an ignition device that performs ignition with the high voltage generated on the secondary side when the primary current of the ignition coil is interrupted. and mask generation means for generating a mask voltage for blocking discharge noise generated by the discharge at a time different from the ion current, and a detection signal of the ion current while the mask voltage is on. A combustion state detection device for an internal combustion engine, comprising a gate means for removing the discharge noise mixed into the detection signal by not outputting the detection signal. 7. Detection means for detecting the ionic current generated after discharge by applying a measurement voltage to the spark plug of an ignition device that performs ignition with the high voltage generated on the secondary side when the primary current of the ignition coil is interrupted. and the first from the rise of the ignition signal.
mask generating means for generating a mask voltage that is turned on only for a predetermined time period and a second predetermined time period from the fall of the ignition signal, and not outputting the detection signal of the ion current while the mask voltage is on; A combustion state detection device for an internal combustion engine, comprising a gate means for removing the discharge noise mixed into the detection signal. 8. Detection means for detecting the ionic current generated after discharge by applying a measurement voltage to the spark plug of an ignition device that performs ignition with the high voltage generated on the secondary side when the primary current of the ignition coil is interrupted. a mask generating means for generating a mask voltage that is turned on for a predetermined period of time from the time when the spark of the ignition plug disappears; and a mask generating means that generates a mask voltage that is turned on for a predetermined period of time from the time when the spark of the spark plug disappears; A combustion state detection device for an internal combustion engine, characterized in that it is provided with a gate means for removing the discharge noise mentioned above. 9. Detection means for detecting the ionic current generated after discharge by applying a measurement voltage to the spark plug of an ignition device that performs ignition with the high voltage generated on the secondary side when the primary current of the ignition coil is interrupted. and mask generation means for generating a mask voltage that is turned on from the time when the ignition signal rises to the time when a predetermined time has elapsed from the time when the ignition signal falls, and not outputting the detection signal of the ion current while the mask voltage is on. A combustion state detection device for an internal combustion engine, comprising: gate means for removing the discharge noise mixed into the detection signal. 10. In place of the gate means, A/D conversion means is provided for A/D converting the ion current detection signal from the detection means, and the mask generation means determines whether the ignition signal is on or not. a first means, and a second means for determining a delay time according to the rotational speed and load of the internal combustion engine when it is determined by the means that the ignition signal is not on.
and a third means for activating the A/D conversion means when a delay time determined by the second means has elapsed from the time when the ignition signal fell from on to off. A combustion state detection device for an internal combustion engine according to any one of claims 6 to 9. 11. The mask generating means includes the first, second and third mask generating means.
11. The combustion state detection device for an internal combustion engine according to claim 10, further comprising a fourth means for operating the A/D conversion means from the time when the spark of the ignition plug stops.