JPH0742922B2 - Ignition timing control device for internal combustion engine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition timing control device for an internal combustion engine (knock control) having a function of detecting knocking occurring in an internal combustion engine and advancing or retarding the ignition timing depending on the state of the knocking. System).

2. Description of the Related Art Conventionally, as a device of this type, a knock pulse signal representing knocking is generated, the number of pulses of the knock pulse signal is counted, and the count value is classified into a predetermined number of pulses in several steps and judged. It is known that the knocking intensity is transferred to the ignition timing calculation device through a small number of signal lines and the retarding process is simplified (Japanese Patent Laid-Open No. 58-5937).
No. 4). However, in this conventional device,
As shown in Fig. 1, the count interval (knock determination interval) of the knock pulse is set by the angle, so at high speed, the interval becomes short in time, while the knock vibration frequency is about 8 KHz. Since the number is constant, the absolute number of knock pulses generated in that section is reduced, and in the case of a certain range of the number of knock pulses, it may not be possible to perform accurate retardation processing according to the knocking intensity.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention provides an ignition timing control device for an internal combustion engine, which can correctly determine the knocking intensity regardless of the change in the rotational speed of the internal combustion engine, and thus can perform an accurate retarding process. The purpose is to

Means for Solving the Problems In the present invention, the threshold for dividing the number of pulse signals is changed according to the change in the number of revolutions, and the knock pulse number range of each knock pulse number range is higher than when the modulus is high when the number of revolutions is low. Reduce the number of judgment pulses.

Embodiment Hereinafter, an ignition timing control device for an internal combustion engine according to the present invention will be described with reference to an embodiment. FIG. 2 is a block diagram of a knotting detection and intensity determination unit, which is a characteristic part of the present invention. In FIG. 2, reference numeral 1 is a knocking detector that detects vibrations, sounds, and the like due to the knocking of the engine, 2 is a filter circuit that passes only the frequency component peculiar to the notking among the detection signals of the notking detector 1, and 5 is the detection signal. It is an AD converter that converts an analog signal into a digital signal. Reference numeral 6 is a micro computer, which is provided with a central processing unit (CPU), a storage device (ROM, RAM), an input / output device (I / O), etc., and responds to a threshold level associated with an AD converter as described later. A timing signal for starting the A / D conversion is given according to the signal from the comparison function to average the output signal (digital signal) of the A / D converter to calculate the notking determination level, and the value of the digital signal within a predetermined period. And a knocking determination level are compared to determine whether knocking is present, and the determination result is output to the ignition timing control device based on an ignition signal from an ignition timing control device (not shown).

Next, an example of a detailed circuit diagram of the above configuration is shown in FIG.
The filter circuit 2 is a bandpass filter circuit including a highpass filter circuit including a capacitor 21 and a resistor 22 and a lowpass filter circuit including a resistor 23 and a capacitor 24. The detection signal from the knocking detector 1 passes through the filter circuit 2 so that the noise component is removed and becomes a sine wave with a knocking frequency near the frequency 8 KHz.
It is input to the analog terminal AN of the one-chip micro-computer 61 which incorporates the -D converter 5 and the micro-computer 6. In this embodiment, MB88413 manufactured by Fujitsu Limited is used as one chip micro computer. A known oscillator 62, a power-on reset circuit 63, and a power supply circuit 64 are connected to the one-chip micro computer 61. Further, an ignition signal (iGt) from an ignition timing control device (not shown) is connected to an interrupt terminal iRQ of one chip microcomputer through a circuit including an input resistor 65, a collector resistor 66 and a transistor 67. The output from the one-chip microcomputer 61 passes through the resistance ladder 69, is D / A converted, and is supplied to the ignition timing control device by the voltage / current converter 68.

Next, the operation of this embodiment will be described with reference to FIGS. 4 to 8. FIG. 4 shows the timing chart of the knocking detection, determination, and retardation amount calculation output of this embodiment. FIG. 5 is a flow chart showing the basic program flow.
In the main routine starting from step 220 of the start, the calculation of the ignition cycle T180 by the built-in timer (step 22
1) Notking in order to obtain the delay time (masking time) T1 until the start of A / D conversion, the time (judgment time) T2 for performing A / D conversion based on the value, and the judgment level to be compared with the A / D conversion value An experimentally determined magnification (k value) for multiplying the average value of the detection signal and an offset value (that is, determination level = average value × k value + offset value) for adding a predetermined value to the average value are calculated. (Step 222).

It is an interrupt input terminal of the 1-chip micro computer 61.
Ignition signal from the ignition timing control device (iG
(t) is inverted by the transistor 67 (210 in FIG. 4) and is input to the microcomputer 61, so that its falling signal (interrupted by the microcomputer in 211 in FIG. 4) (211-1 in FIG. 5). After starting the interrupt routine, the microcomputer waits for AD conversion during the masking time T1 (FIG. 213) following the interrupt process (FIG. 4 212) (FIG. 5).
213-1). After the masking time ends, time T2 (Fig.
4) The A-D conversion is repeatedly performed for the value of time, and the A-D conversion value V _AD for each time and the cylinder-by-cylinder judgment level V _{LEV of the} previous calculation
In comparison, when V _LEV <V _AD , the knock pulse is counted up (214-3 in FIG. 5). After conversion, AD
The average value of the converter is calculated at the timing shown in FIG. 215, and the cylinder-by-cylinder judgment level for the next judgment section is calculated according to the k value and the offset value. The judgment result (a judgment procedure will be described later) is output to the 8-bit port of the microcomputer at the timing of 216 in FIG. 4 (216-1 in FIG. 5), and the D-A conversion is performed by passing through the resistance ladder. The analog value is converted into a current by the voltage / current converter and output to an ignition timing control device (not shown). The judgment output is represented by the retard amount.

Next, a detailed description of the operation of the A-D conversion part and the strength determination part which is the main part of the present invention will be given with reference to FIGS.

This corresponds to one cycle of the detection signal shown in FIG. As described above, the detected signal is an 8 KHz sine wave. Referring to FIG. 7, when the A-D conversion program is started (step 320), the mode of the comparator, which is a comparison function in one chip microcomputer, is designated, and the threshold level Th is changed from 0 level. It is set (step 321).
Then start the comparator (step 322,
The falling time TDO of Th of the sine wave 301 from Th is detected (step
323-1), further check the Th level for the purpose of preventing malfunction (step 323-2). After detecting the Th level, move to the routine for detecting the rising from the Th level (step 32
5) Then, the rise detection time TZ1 is delayed by a predetermined time ΔD (step 326) to reach time TS1. In the rising edge detection routine (step 325), the judgments are arranged in series so that even if the rising edge is not detected, the process is finally moved to step 326 so that the arithmetic processing does not fall into an infinite loop. Then, a sine wave 3 that starts AD conversion from time TS1
It is set around the peak 310-1 of 01. that time,
The slope near the peak of the sine wave 301 is the rising edge of the sine wave,
The peak value V _P of the sine wave 301 is obtained even if A-D conversion is performed by delaying the delay time ΔD to near the peak, as compared with the falling slope. That value VS1 given by the conversion start time TS1, the value VF1 given by the end time TF1 are both compared with the peak value V _P, the difference is very small, yet in the present example A-D converter successive approximation type A
The AD conversion value obtained by using -D conversion is VS1, V
It is closer to V than F1. The obtained conversion value is read and stored in the memory (step 328), and the next operation step 329 is carried out.

FIG. 8 is a flow chart for strength judgment, which is the main part of the present invention.

The _AD -converted value V _AD is compared with the cylinder-by-cylinder determination level V _LEV (215-2) obtained up to the previous time (step 33).
1) When the A-D conversion value is lower than the cylinder-specific determination level V _LEV , the operation proceeds to the next operation step 337. Cylinder judgment level V
When it is larger than _LEV, that is, when it is determined that a knock is present, 1 is added to the knock pulse counter, and the intensity corresponding to the pulse number is determined from the table of two or more knock intensities based on the rotation speed (steps 334, 335). ).

Note that the table of the knock intensity is, for example, the knock intensity according to each knock pulse number range, “no knock”,
It is divided into four stages: “small knock”, “medium knock”, and “large knock”. As shown in FIG.
In the range <3000) and the high speed range (Ne ≧ 3000), the range of the number of knock pulses, which is the threshold for dividing the case, is changed. As a result, the absolute number of knock pulses in the knock determination section changes from low speed to high speed. Is being corrected.

The obtained knock strength is read (step 336) and the operation proceeds to the next operation step 337.

EFFECTS OF THE INVENTION The present invention is to change the threshold value of the case classification for determining the knocking intensity according to the number of revolutions, and to reduce the number of determination pulses in each knock pulse number range when the number of revolutions is higher than when it is low. By correcting the change in the absolute number of knock pulses in the knock determination section that can change according to the number of revolutions, the knocking intensity is accurately determined without being affected by the change in the number of revolutions, and the retard angle amount is determined. From low speed to high speed,
Stable knock control is possible.

Further, when the threshold for dividing cases is set so as to be proportional to the reciprocal of the number of revolutions of the internal combustion engine, it is not necessary to have a table of thresholds for each number of revolutions, and an appropriate threshold can be obtained. There is an advantage.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the change of the judgment section due to the change of the rotation speed and the number of knock pulses, FIG. 2 is an overall configuration diagram showing an embodiment of the present invention, and FIG. FIG. 4 is a detailed configuration diagram, FIG. 4 is a timing chart schematically showing the processing timing in the apparatus shown in FIG. 2, and FIGS. 5, 7 and 8 are flow charts showing the processing procedure in the microcomputer. FIG. 6 is a diagram showing the timing of AD conversion in the apparatus shown in FIG. 2. FIG. 9 is a diagram showing case classification of the knock pulse. In the figure, 1 ... notting detector, 2 ... filter circuit, 5 ...
... A-D converter, 6 ... Microcomputer

Claims (2)

[Claims] 1. A knocking detector for detecting knocking generated in an internal combustion engine, and an output signal of the knocking detector is compared with a determination level over a predetermined crank angle section to generate a pulse number according to the strength of knocking. For an internal combustion engine that includes a device and a device that counts the number of pulses and determines the knock intensity by dividing the number of pulses into a predetermined pulse number range, and changes the addition amount of knock correction of the ignition timing according to the knock intensity. In the ignition timing control device, the number of determination pulses in each knock pulse number range is changed when the number of pulses for performing the above knock intensity determination is changed depending on the number of revolutions of the internal combustion engine, when the number of revolutions is higher than when it is low. An ignition timing control device for an internal combustion engine, characterized in that 2. The ignition timing control device for an internal combustion engine according to claim 1, wherein the change in the threshold value is proportional to the reciprocal of the rotational speed of the internal combustion engine.